FormationVegetableMould.txt

THE FORMATION OF VEGETABLE MOULD
THROUGH THE ACTION OF WORMS
WITH OBSERVATIONS ON THEIR HABITS.

by Charles Darwin




INTRODUCTION.



The share which worms have taken in the formation of the layer of 
vegetable mould, which covers the whole surface of the land in 
every moderately humid country, is the subject of the present 
volume.  This mould is generally of a blackish colour and a few 
inches in thickness.  In different districts it differs but little 
in appearance, although it may rest on various subsoils.  The 
uniform fineness of the particles of which it is composed is one of 
its chief characteristic features; and this may be well observed in 
any gravelly country, where a recently-ploughed field immediately 
adjoins one which has long remained undisturbed for pasture, and 
where the vegetable mould is exposed on the sides of a ditch or 
hole.  The subject may appear an insignificant one, but we shall 
see that it possesses some interest; and the maxim "de minimis non 
curat lex," does not apply to science.  Even Elie de Beaumont, who 
generally undervalues small agencies and their accumulated effects, 
remarks:  {1} "La couche tres-mince de la terre vegetale est un 
monument d'une haute antiquite, et, par le fait de sa permanence, 
un objet digne d'occuper le geologue, et capable de lui fournir des 
remarques interessantes."  Although the superficial layer of 
vegetable mould as a whole no doubt is of the highest antiquity, 
yet in regard to its permanence, we shall hereafter see reason to 
believe that its component particles are in most cases removed at 
not a very slow rate, and are replaced by others due to the 
disintegration of the underlying materials.

As I was led to keep in my study during many months worms in pots 
filled with earth, I became interested in them, and wished to learn 
how far they acted consciously, and how much mental power they 
displayed.  I was the more desirous to learn something on this 
head, as few observations of this kind have been made, as far as I 
know, on animals so low in the scale of organization and so poorly 
provided with sense-organs, as are earth-worms.

In the year 1837, a short paper was read by me before the 
Geological Society of London, {2} "On the Formation of Mould," in 
which it was shown that small fragments of burnt marl, cinders, 
&c., which had been thickly strewed over the surface of several 
meadows, were found after a few years lying at the depth of some 
inches beneath the turf, but still forming a layer.  This apparent 
sinking of superficial bodies is due, as was first suggested to me 
by Mr. Wedgwood of Maer Hall in Staffordshire, to the large 
quantity of fine earth continually brought up to the surface by 
worms in the form of castings.  These castings are sooner or later 
spread out and cover up any object left on the surface.  I was thus 
led to conclude that all the vegetable mould over the whole country 
has passed many times through, and will again pass many times 
through, the intestinal canals of worms.  Hence the term "animal 
mould" would be in some respects more appropriate than that 
commonly used of "vegetable mould."

Ten years after the publication of my paper, M. D'Archiac, 
evidently influenced by the doctrines of Elie de Beaumont, wrote 
about my "singuliere theorie," and objected that it could apply 
only to "les prairies basses et humides;" and that "les terres 
labourees, les bois, les prairies elevees, n'apportent aucune 
preuve a l'appui de cette maniere de voir." {3}  But M. D'Archiac 
must have thus argued from inner consciousness and not from 
observation, for worms abound to an extraordinary degree in kitchen 
gardens where the soil is continually worked, though in such loose 
soil they generally deposit their castings in any open cavities or 
within their old burrows instead of on the surface.  Hensen 
estimates that there are about twice as many worms in gardens as in 
corn-fields. {4}  With respect to "prairies elevees," I do not know 
how it may be in France, but nowhere in England have I seen the 
ground so thickly covered with castings as on commons, at a height 
of several hundred feet above the sea.  In woods again, if the 
loose leaves in autumn are removed, the whole surface will be found 
strewed with castings.  Dr. King, the superintendent of the Botanic 
Garden in Calcutta, to whose kindness I am indebted for many 
observations on earth-worms, informs me that he found, near Nancy 
in France, the bottom of the State forests covered over many acres 
with a spongy layer, composed of dead leaves and innumerable worm-
castings.  He there heard the Professor of "Amenagement des Forets" 
lecturing to his pupils, and pointing out this case as a "beautiful 
example of the natural cultivation of the soil; for year after year 
the thrown-up castings cover the dead leaves; the result being a 
rich humus of great thickness."

In the year 1869, Mr. Fish {5} rejected my conclusions with respect 
to the part which worms have played in the formation of vegetable 
mould, merely on account of their assumed incapacity to do so much 
work.  He remarks that "considering their weakness and their size, 
the work they are represented to have accomplished is stupendous."  
Here we have an instance of that inability to sum up the effects of 
a continually recurrent cause, which has often retarded the 
progress of science, as formerly in the case of geology, and more 
recently in that of the principle of evolution.

Although these several objections seemed to me to have no weight, 
yet I resolved to make more observations of the same kind as those 
published, and to attack the problem on another side; namely, to 
weigh all the castings thrown up within a given time in a measured 
space, instead of ascertaining the rate at which objects left on 
the surface were buried by worms.  But some of my observations have 
been rendered almost superfluous by an admirable paper by Hensen, 
already alluded to, which appeared in 1877. {6}  Before entering on 
details with respect to the castings, it will be advisable to give 
some account of the habits of worms from my own observations and 
from those of other naturalists.

[FIRST EDITION, October 10th, 1881.]



CHAPTER I--HABITS OF WORMS.



Nature of the sites inhabited--Can live long under water--
Nocturnal--Wander about at night--Often lie close to the mouths of 
their burrows, and are thus destroyed in large numbers by birds--
Structure--Do not possess eyes, but can distinguish between light 
and darkness--Retreat rapidly when brightly illuminated, not by a 
reflex action--Power of attention--Sensitive to heat and cold--
Completely deaf--Sensitive to vibrations and to touch--Feeble power 
of smell--Taste--Mental qualities--Nature of food--Omnivorous--
Digestion--Leaves before being swallowed, moistened with a fluid of 
the nature of the pancreatic secretion--Extra-stomachal digestion--
Calciferous glands, structure of--Calcareous concretions formed in 
the anterior pair of glands--The calcareous matter primarily an 
excretion, but secondarily serves to neutralise the acids generated 
during the digestive process.


Earth-worms are distributed throughout the world under the form of 
a few genera, which externally are closely similar to one another.  
The British species of Lumbricus have never been carefully 
monographed; but we may judge of their probable number from those 
inhabiting neighbouring countries.  In Scandinavia there are eight 
species, according to Eisen; {7} but two of these rarely burrow in 
the ground, and one inhabits very wet places or even lives under 
the water.  We are here concerned only with the kinds which bring 
up earth to the surface in the form of castings.  Hoffmeister says 
that the species in Germany are not well known, but gives the same 
number as Eisen, together with some strongly marked varieties. {8}

Earth-worms abound in England in many different stations.  Their 
castings may be seen in extraordinary numbers on commons and chalk-
downs, so as almost to cover the whole surface, where the soil is 
poor and the grass short and thin.  But they are almost or quite as 
numerous in some of the London parks, where the grass grows well 
and the soil appears rich.  Even on the same field worms are much 
more frequent in some places than in others, without any visible 
difference in the nature of the soil.  They abound in paved court-
yards close to houses; and an instance will be given in which they 
had burrowed through the floor of a very damp cellar.  I have seen 
worms in black peat in a boggy field; but they are extremely rare, 
or quite absent in the drier, brown, fibrous peat, which is so much 
valued by gardeners.  On dry, sandy or gravelly tracks, where heath 
with some gorse, ferns, coarse grass, moss and lichens alone grow, 
hardly any worms can be found.  But in many parts of England, 
wherever a path crosses a heath, its surface becomes covered with a 
fine short sward.  Whether this change of vegetation is due to the 
taller plants being killed by the occasional trampling of man and 
animals, or to the soil being occasionally manured by the droppings 
from animals, I do not know. {9}  On such grassy paths worm-
castings may often be seen.  On a heath in Surrey, which was 
carefully examined, there were only a few castings on these paths, 
where they were much inclined; but on the more level parts, where a 
bed of fine earth had been washed down from the steeper parts and 
had accumulated to a thickness of a few inches, worm-castings 
abounded.  These spots seemed to be overstocked with worms, so that 
they had been compelled to spread to a distance of a few feet from 
the grassy paths, and here their castings had been thrown up among 
the heath; but beyond this limit, not a single casting could be 
found.  A layer, though a thin one, of fine earth, which probably 
long retains some moisture, is in all cases, as I believe, 
necessary for their existence; and the mere compression of the soil 
appears to be in some degree favourable to them, for they often 
abound in old gravel walks, and in foot-paths across fields.

Beneath large trees few castings can be found during certain 
seasons of the year, and this is apparently due to the moisture 
having been sucked out of the ground by the innumerable roots of 
the trees; for such places may be seen covered with castings after 
the heavy autumnal rains.  Although most coppices and woods support 
many worms, yet in a forest of tall and ancient beech-trees in 
Knole Park, where the ground beneath was bare of all vegetation, 
not a single casting could be found over wide spaces, even during 
the autumn.  Nevertheless, castings were abundant on some grass-
covered glades and indentations which penetrated this forest.  On 
the mountains of North Wales and on the Alps, worms, as I have been 
informed, are in most places rare; and this may perhaps be due to 
the close proximity of the subjacent rocks, into which worms cannot 
burrow during the winter so as to escape being frozen.  Dr. 
McIntosh, however, found worm-castings at a height of 1500 feet on 
Schiehallion in Scotland.  They are numerous on some hills near 
Turin at from 2000 to 3000 feet above the sea, and at a great 
altitude on the Nilgiri Mountains in South India and on the 
Himalaya.

Earth-worms must be considered as terrestrial animals, though they 
are still in one sense semi-aquatic, like the other members of the 
great class of annelids to which they belong.  M. Perrier found 
that their exposure to the dry air of a room for only a single 
night was fatal to them.  On the other hand he kept several large 
worms alive for nearly four months, completely submerged in water. 
{10}  During the summer when the ground is dry, they penetrate to a 
considerable depth and cease to work, as they do during the winter 
when the ground is frozen.  Worms are nocturnal in their habits, 
and at night may be seen crawling about in large numbers, but 
usually with their tails still inserted in their burrows.  By the 
expansion of this part of their bodies, and with the help of the 
short, slightly reflexed bristles, with which their bodies are 
armed, they hold so fast that they can seldom be dragged out of the 
ground without being torn into pieces. {11}  During the day they 
remain in their burrows, except at the pairing season, when those 
which inhabit adjoining burrows expose the greater part of their 
bodies for an hour or two in the early morning.  Sick individuals, 
which are generally affected by the parasitic larvae of a fly, must 
also be excepted, as they wander about during the day and die on 
the surface.  After heavy rain succeeding dry weather, an 
astonishing number of dead worms may sometimes be seen lying on the 
ground.  Mr. Galton informs me that on one such occasion (March, 
1881), the dead worms averaged one for every two and a half paces 
in length on a walk in Hyde Park, four paces in width.  He counted 
no less than 45 dead worms in one place in a length of sixteen 
paces.  From the facts above given, it is not probable that these 
worms could have been drowned, and if they had been drowned they 
would have perished in their burrows.  I believe that they were 
already sick, and that their deaths were merely hastened by the 
ground being flooded.

It has often been said that under ordinary circumstances healthy 
worms never, or very rarely, completely leave their burrows at 
night; but this is an error, as White of Selborne long ago knew.  
In the morning, after there has been heavy rain, the film of mud or 
of very fine sand over gravel-walks is often plainly marked with 
their tracks.  I have noticed this from August to May, both months 
included, and it probably occurs during the two remaining months of 
the year when they are wet.  On these occasions, very few dead 
worms could anywhere be seen.  On January 31, 1881, after a long-
continued and unusually severe frost with much snow, as soon as a 
thaw set in, the walks were marked with innumerable tracks.  On one 
occasion, five tracks were counted crossing a space of only an inch 
square.  They could sometimes be traced either to or from the 
mouths of the burrows in the gravel-walks, for distances between 2 
or 3 up to 15 yards.  I have never seen two tracks leading to the 
same burrow; nor is it likely, from what we shall presently see of 
their sense-organs, that a worm could find its way back to its 
burrow after having once left it.  They apparently leave their 
burrows on a voyage of discovery, and thus they find new sites to 
inhabit.

Morren states {12} that worms often lie for hours almost motionless 
close beneath the mouths of their burrows.  I have occasionally 
noticed the same fact with worms kept in pots in the house; so that 
by looking down into their burrows, their heads could just be seen.  
If the ejected earth or rubbish over the burrows be suddenly 
removed, the end of the worm's body may very often be seen rapidly 
retreating.  This habit of lying near the surface leads to their 
destruction to an immense extent.  Every morning during certain 
seasons of the year, the thrushes and blackbirds on all the lawns 
throughout the country draw out of their holes an astonishing 
number of worms, and this they could not do, unless they lay close 
to the surface.  It is not probable that worms behave in this 
manner for the sake of breathing fresh air, for we have seen that 
they can live for a long time under water.  I believe that they lie 
near the surface for the sake of warmth, especially in the morning; 
and we shall hereafter find that they often coat the mouths of 
their burrows with leaves, apparently to prevent their bodies from 
coming into close contact with the cold damp earth.  It is said 
that they completely close their burrows during the winter.

Structure.--A few remarks must be made on this subject.  The body 
of a large worm consists of from 100 to 200 almost cylindrical 
rings or segments, each furnished with minute bristles.  The 
muscular system is well developed.  Worms can crawl backwards as 
well as forwards, and by the aid of their affixed tails can retreat 
with extraordinary rapidity into their burrows.  The mouth is 
situated at the anterior end of the body, and is provided with a 
little projection (lobe or lip, as it has been variously called) 
which is used for prehension.  Internally, behind the mouth, there 
is a strong pharynx, shown in the accompanying diagram (Fig. 1) 
which is pushed forwards when the animal eats, and this part 
corresponds, according to Perrier, with the protrudable trunk or 
proboscis of other annelids.  The pharynx leads into the 
oesophagus, on each side of which in the lower part there are three 
pairs of large glands, which secrete a surprising amount of 
carbonate of lime.  These calciferous glands are highly remarkable, 
for nothing like them is known in any other animal.  Their use will 
be discussed when we treat of the digestive process.  In most of 
the species, the oesophagus is enlarged into a crop in front of the 
gizzard.  This latter organ is lined with a smooth thick chitinous 
membrane, and is surrounded by weak longitudinal, but powerful 
transverse muscles.  Perrier saw these muscles in energetic action; 
and, as he remarks, the trituration of the food must be chiefly 
effected by this organ, for worms possess no jaws or teeth of any 
kind.  Grains of sand and small stones, from the 1/20 to a little 
more than the 1/10 inch in diameter, may generally be found in 
their gizzards and intestines.  As it is certain that worms swallow 
many little stones, independently of those swallowed while 
excavating their burrows, it is probable that they serve, like 
mill-stones, to triturate their food.  The gizzard opens into the 
intestine, which runs in a straight course to the vent at the 
posterior end of the body.  The intestine presents a remarkable 
structure, the typhlosolis, or, as the old anatomists called it, an 
intestine within an intestine; and Claparede {13} has shown that 
this consists of a deep longitudinal involution of the walls of the 
intestine, by which means an extensive absorbent surface is gained.

The circulatory system is well developed.  Worms breathe by their 
skin, as they do not possess any special respiratory organs.  The 
two sexes are united in the same individual, but two individuals 
pair together.  The nervous system is fairly well developed; and 
the two almost confluent cerebral ganglia are situated very near to 
the anterior end of the body.

Senses.--Worms are destitute of eyes, and at first I thought that 
they were quite insensible to light; for those kept in confinement 
were repeatedly observed by the aid of a candle, and others out of 
doors by the aid of a lantern, yet they were rarely alarmed, 
although extremely timid animals.  Other persons have found no 
difficulty in observing worms at night by the same means. {14}

Hoffmeister, however, states {15} that worms, with the exception of 
a few individuals, are extremely sensitive to light; but he admits 
that in most cases a certain time is requisite for its action.  
These statements led me to watch on many successive nights worms 
kept in pots, which were protected from currents of air by means of 
glass plates.  The pots were approached very gently, in order that 
no vibration of the floor should be caused.  When under these 
circumstances worms were illuminated by a bull's-eye lantern having 
slides of dark red and blue glass, which intercepted so much light 
that they could be seen only with some difficulty, they were not at 
all affected by this amount of light, however long they were 
exposed to it.  The light, as far as I could judge, was brighter 
than that from the full moon.  Its colour apparently made no 
difference in the result.  When they were illuminated by a candle, 
or even by a bright paraffin lamp, they were not usually affected 
at first.  Nor were they when the light was alternately admitted 
and shut off.  Sometimes, however, they behaved very differently, 
for as soon as the light fell on them, they withdrew into their 
burrows with almost instantaneous rapidity.  This occurred perhaps 
once out of a dozen times.  When they did not withdraw instantly, 
they often raised the anterior tapering ends of their bodies from 
the ground, as if their attention was aroused or as if surprise was 
felt; or they moved their bodies from side to side as if feeling 
for some object.  They appeared distressed by the light; but I 
doubt whether this was really the case, for on two occasions after 
withdrawing slowly, they remained for a long time with their 
anterior extremities protruding a little from the mouths of their 
burrows, in which position they were ready for instant and complete 
withdrawal.

When the light from a candle was concentrated by means of a large 
lens on the anterior extremity, they generally withdrew instantly; 
but this concentrated light failed to act perhaps once out of half 
a dozen trials.  The light was on one occasion concentrated on a 
worm lying beneath water in a saucer, and it instantly withdrew 
into its burrow.  In all cases the duration of the light, unless 
extremely feeble, made a great difference in the result; for worms 
left exposed before a paraffin lamp or a candle invariably 
retreated into their burrows within from five to fifteen minutes; 
and if in the evening the pots were illuminated before the worms 
had come out of their burrows, they failed to appear.

From the foregoing facts it is evident that light affects worms by 
its intensity and by its duration.  It is only the anterior 
extremity of the body, where the cerebral ganglia lie, which is 
affected by light, as Hoffmeister asserts, and as I observed on 
many occasions.  If this part is shaded, other parts of the body 
may be fully illuminated, and no effect will be produced.  As these 
animals have no eyes, we must suppose that the light passes through 
their skins, and in some manner excites their cerebral ganglia.  It 
appeared at first probable that the different manner in which they 
were affected on different occasions might be explained, either by 
the degree of extension of their skin and its consequent 
transparency, or by some particular incident of the light; but I 
could discover no such relation.  One thing was manifest, namely, 
that when worms were employed in dragging leaves into their burrows 
or in eating them, and even during the short intervals whilst they 
rested from their work, they either did not perceive the light or 
were regardless of it; and this occurred even when the light was 
concentrated on them through a large lens.  So, again, whilst they 
are paired, they will remain for an hour or two out of their 
burrows, fully exposed to the morning light; but it appears from 
what Hoffmeister says that a light will occasionally cause paired 
individuals to separate.

When a worm is suddenly illuminated and dashes like a rabbit into 
its burrow--to use the expression employed by a friend--we are at 
first led to look at the action as a reflex one.  The irritation of 
the cerebral ganglia appears to cause certain muscles to contract 
in an inevitable manner, independently of the will or consciousness 
of the animal, as if it were an automaton.  But the different 
effect which a light produced on different occasions, and 
especially the fact that a worm when in any way employed and in the 
intervals of such employment, whatever set of muscles and ganglia 
may then have been brought into play, is often regardless of light, 
are opposed to the view of the sudden withdrawal being a simple 
reflex action.  With the higher animals, when close attention to 
some object leads to the disregard of the impressions which other 
objects must be producing on them, we attribute this to their 
attention being then absorbed; and attention implies the presence 
of a mind.  Every sportsman knows that he can approach animals 
whilst they are grazing, fighting or courting, much more easily 
than at other times.  The state, also, of the nervous system of the 
higher animals differs much at different times, for instance, a 
horse is much more readily startled at one time than at another.  
The comparison here implied between the actions of one of the 
higher animals and of one so low in the scale as an earth-worm, may 
appear far-fetched; for we thus attribute to the worm attention and 
some mental power, nevertheless I can see no reason to doubt the 
justice of the comparison.

Although worms cannot be said to possess the power of vision, their 
sensitiveness to light enables them to distinguish between day and 
night; and they thus escape extreme danger from the many diurnal 
animals which prey on them.  Their withdrawal into their burrows 
during the day appears, however, to have become an habitual action; 
for worms kept in pots covered by glass plates, over which sheets 
of black paper were spread, and placed before a north-east window, 
remained during the day-time in their burrows and came out every 
night; and they continued thus to act for a week.  No doubt a 
little light may have entered between the sheets of glass and the 
blackened paper; but we know from the trials with coloured glass, 
that worms are indifferent to a small amount of light.

Worms appear to be less sensitive to moderate radiant heat than to 
a bright light.  I judge of this from having held at different 
times a poker heated to dull redness near some worms, at a distance 
which caused a very sensible degree of warmth in my hand.  One of 
them took no notice; a second withdrew into its burrow, but not 
quickly; the third and fourth much more quickly, and the fifth as 
quickly as possible.  The light from a candle, concentrated by a 
lens and passing through a sheet of glass which would intercept 
most of the heat-rays, generally caused a much more rapid retreat 
than did the heated poker.  Worms are sensitive to a low 
temperature, as may be inferred from their not coming out of their 
burrows during a frost.

Worms do not possess any sense of hearing.  They took not the least 
notice of the shrill notes from a metal whistle, which was 
repeatedly sounded near them; nor did they of the deepest and 
loudest tones of a bassoon.  They were indifferent to shouts, if 
care was taken that the breath did not strike them.  When placed on 
a table close to the keys of a piano, which was played as loudly as 
possible, they remained perfectly quiet.

Although they are indifferent to undulations in the air audible by 
us, they are extremely sensitive to vibrations in any solid object.  
When the pots containing two worms which had remained quite 
indifferent to the sound of the piano, were placed on this 
instrument, and the note C in the bass clef was struck, both 
instantly retreated into their burrows.  After a time they emerged, 
and when G above the line in the treble clef was struck they again 
retreated.  Under similar circumstances on another night one worm 
dashed into its burrow on a very high note being struck only once, 
and the other worm when C in the treble clef was struck.  On these 
occasions the worms were not touching the sides of the pots, which 
stood in saucers; so that the vibrations, before reaching their 
bodies, had to pass from the sounding board of the piano, through 
the saucer, the bottom of the pot and the damp, not very compact 
earth on which they lay with their tails in their burrows.  They 
often showed their sensitiveness when the pot in which they lived, 
or the table on which the pot stood, was accidentally and lightly 
struck; but they appeared less sensitive to such jars than to the 
vibrations of the piano; and their sensitiveness to jars varied 
much at different times.

It has often been said that if the ground is beaten or otherwise 
made to tremble, worms believe that they are pursued by a mole and 
leave their burrows.  From one account that I have received, I have 
no doubt that this is often the case; but a gentleman informs me 
that he lately saw eight or ten worms leave their burrows and crawl 
about the grass on some boggy land on which two men had just 
trampled while setting a trap; and this occurred in a part of 
Ireland where there were no moles.  I have been assured by a 
Volunteer that he has often seen many large earth-worms crawling 
quickly about the grass, a few minutes after his company had fired 
a volley with blank cartridges.  The Peewit (Tringa vanellus, 
Linn.) seems to know instinctively that worms will emerge if the 
ground is made to tremble; for Bishop Stanley states (as I hear 
from Mr. Moorhouse) that a young peewit kept in confinement used to 
stand on one leg and beat the turf with the other leg until the 
worms crawled out of their burrows, when they were instantly 
devoured.  Nevertheless, worms do not invariably leave their 
burrows when the ground is made to tremble, as I know by having 
beaten it with a spade, but perhaps it was beaten too violently.

The whole body of a worm is sensitive to contact.  A slight puff of 
air from the mouth causes an instant retreat.  The glass plates 
placed over the pots did not fit closely, and blowing through the 
very narrow chinks thus left, often sufficed to cause a rapid 
retreat.  They sometimes perceived the eddies in the air caused by 
quickly removing the glass plates.  When a worm first comes out of 
its burrow, it generally moves the much extended anterior extremity 
of its body from side to side in all directions, apparently as an 
organ of touch; and there is some reason to believe, as we shall 
see in the next chapter, that they are thus enabled to gain a 
general notion of the form of an object.  Of all their senses that 
of touch, including in this term the perception of a vibration, 
seems much the most highly developed.

In worms the sense of smell apparently is confined to the 
perception of certain odours, and is feeble.  They were quite 
indifferent to my breath, as long as I breathed on them very 
gently.  This was tried, because it appeared possible that they 
might thus be warned of the approach of an enemy.  They exhibited 
the same indifference to my breath whilst I chewed some tobacco, 
and while a pellet of cotton-wool with a few drops of millefleurs 
perfume or of acetic acid was kept in my mouth.  Pellets of cotton-
wool soaked in tobacco juice, in millefleurs perfume, and in 
paraffin, were held with pincers and were waved about within two or 
three inches of several worms, but they took no notice.  On one or 
two occasions, however, when acetic acid had been placed on the 
pellets, the worms appeared a little uneasy, and this was probably 
due to the irritation of their skins.  The perception of such 
unnatural odours would be of no service to worms; and as such timid 
creatures would almost certainly exhibit some signs of any new 
impression, we may conclude that they did not perceive these 
odours.

The result was different when cabbage-leaves and pieces of onion 
were employed, both of which are devoured with much relish by 
worms.  Small square pieces of fresh and half-decayed cabbage-
leaves and of onion bulbs were on nine occasions buried in my pots, 
beneath about 0.25 of an inch of common garden soil; and they were 
always discovered by the worms.  One bit of cabbage was discovered 
and removed in the course of two hours; three were removed by the 
next morning, that is, after a single night; two others after two 
nights; and the seventh bit after three nights.  Two pieces of 
onion were discovered and removed after three nights.  Bits of 
fresh raw meat, of which worms are very fond, were buried, and were 
not discovered within forty-eight hours, during which time they had 
not become putrid.  The earth above the various buried objects was 
generally pressed down only slightly, so as not to prevent the 
emission of any odour.  On two occasions, however, the surface was 
well watered, and was thus rendered somewhat compact.  After the 
bits of cabbage and onion had been removed, I looked beneath them 
to see whether the worms had accidentally come up from below, but 
there was no sign of a burrow; and twice the buried objects were 
laid on pieces of tin-foil which were not in the least displaced.  
It is of course possible that the worms whilst moving about on the 
surface of the ground, with their tails affixed within their 
burrows, may have poked their heads into the places where the above 
objects were buried; but I have never seen worms acting in this 
manner.  Some pieces of cabbage-leaf and of onion were twice buried 
beneath very fine ferruginous sand, which was slightly pressed down 
and well watered, so as to be rendered very compact, and these 
pieces were never discovered.  On a third occasion the same kind of 
sand was neither pressed down nor watered, and the pieces of 
cabbage were discovered and removed after the second night.  These 
several facts indicate that worms possess some power of smell; and 
that they discover by this means odoriferous and much-coveted kinds 
of food.

It may be presumed that all animals which feed on various 
substances possess the sense of taste, and this is certainly the 
case with worms.  Cabbage-leaves are much liked by worms; and it 
appears that they can distinguish between different varieties; but 
this may perhaps be owing to differences in their texture.  On 
eleven occasions pieces of the fresh leaves of a common green 
variety and of the red variety used for pickling were given them, 
and they preferred the green, the red being either wholly neglected 
or much less gnawed.  On two other occasions, however, they seemed 
to prefer the red.  Half-decayed leaves of the red variety and 
fresh leaves of the green were attacked about equally.  When leaves 
of the cabbage, horse-radish (a favourite food) and of the onion 
were given together, the latter were always, and manifestly 
preferred.  Leaves of the cabbage, lime-tree, Ampelopsis, parsnip 
(Pastinaca), and celery (Apium) were likewise given together; and 
those of the celery were first eaten.  But when leaves of cabbage, 
turnip, beet, celery, wild cherry and carrots were given together, 
the two latter kinds, especially those of the carrot, were 
preferred to all the others, including those of celery.  It was 
also manifest after many trials that wild cherry leaves were 
greatly preferred to those of the lime-tree and hazel (Corylus).  
According to Mr. Bridgman the half-decayed leaves of Phlox verna 
are particularly liked by worms. {16}

Pieces of the leaves of cabbage, turnip, horse-radish and onion 
were left on the pots during 22 days, and were all attacked and had 
to be renewed; but during the whole of this time leaves of an 
Artemisia and of the culinary sage, thyme and mint, mingled with 
the above leaves, were quite neglected excepting those of the mint, 
which were occasionally and very slightly nibbled.  These latter 
four kinds of leaves do not differ in texture in a manner which 
could make them disagreeable to worms; they all have a strong 
taste, but so have the four first mentioned kinds of leaves; and 
the wide difference in the result must be attributed to a 
preference by the worms for one taste over another.

Mental Qualities.--There is little to be said on this head.  We 
have seen that worms are timid.  It may be doubted whether they 
suffer as much pain when injured, as they seem to express by their 
contortions.  Judging by their eagerness for certain kinds of food, 
they must enjoy the pleasure of eating.  Their sexual passion is 
strong enough to overcome for a time their dread of light.  They 
perhaps have a trace of social feeling, for they are not disturbed 
by crawling over each other's bodies, and they sometimes lie in 
contact.  According to Hoffmeister they pass the winter either 
singly or rolled up with others into a ball at the bottom of their 
burrows. {17}  Although worms are so remarkably deficient in the 
several sense-organs, this does not necessarily preclude 
intelligence, as we know from such cases as those of Laura 
Bridgman; and we have seen that when their attention is engaged, 
they neglect impressions to which they would otherwise have 
attended; and attention indicates the presence of a mind of some 
kind.  They are also much more easily excited at certain times than 
at others.  They perform a few actions instinctively, that is, all 
the individuals, including the young, perform such actions in 
nearly the same fashion.  This is shown by the manner in which the 
species of Perichaeta eject their castings, so as to construct 
towers; also by the manner in which the burrows of the common 
earth-worm are smoothly lined with fine earth and often with little 
stones, and the mouths of their burrows with leaves.  One of their 
strongest instincts is the plugging up the mouths of their burrows 
with various objects; and very young worms act in this manner.  But 
some degree of intelligence appears, as we shall see in the next 
chapter, to be exhibited in this work,--a result which has 
surprised me more than anything else in regard to worms.

Food and Digestion.--Worms are omnivorous.  They swallow an 
enormous quantity of earth, out of which they extract any 
digestible matter which it may contain; but to this subject I must 
recur.  They also consume a large number of half-decayed leaves of 
all kinds, excepting a few which have an unpleasant taste or are 
too tough for them; likewise petioles, peduncles, and decayed 
flowers.  But they will also consume fresh leaves, as I have found 
by repeated trials.  According to Morren {18} they will eat 
particles of sugar and liquorice; and the worms which I kept drew 
many bits of dry starch into their burrows, and a large bit had its 
angles well rounded by the fluid poured out of their mouths.  But 
as they often drag particles of soft stone, such as of chalk, into 
their burrows, I feel some doubt whether the starch was used as 
food.  Pieces of raw and roasted meat were fixed several times by 
long pins to the surface of the soil in my pots, and night after 
night the worms could be seen tugging at them, with the edges of 
the pieces engulfed in their mouths, so that much was consumed.  
Raw fat seems to be preferred even to raw meat or to any other 
substance which was given them, and much was consumed.  They are 
cannibals, for the two halves of a dead worm placed in two of the 
pots were dragged into the burrows and gnawed; but as far as I 
could judge, they prefer fresh to putrid meat, and in so far I 
differ from Hoffmeister.

Leon Fredericq states {19} that the digestive fluid of worms is of 
the same nature as the pancreatic secretion of the higher animals; 
and this conclusion agrees perfectly with the kinds of food which 
worms consume.  Pancreatic juice emulsifies fat, and we have just 
seen how greedily worms devour fat; it dissolves fibrin, and worms 
eat raw meat; it converts starch into grape-sugar with wonderful 
rapidity, and we shall presently show that the digestive fluid of 
worms acts on starch. {20}  But they live chiefly on half-decayed 
leaves; and these would be useless to them unless they could digest 
the cellulose forming the cell-walls; for it is well known that all 
other nutritious substances are almost completely withdrawn from 
leaves, shortly before they fall off.  It has, however, now been 
ascertained that some forms of cellulose, though very little or not 
at all attacked by the gastric secretion of the higher animals, are 
acted on by that from the pancreas. {21}

The half-decayed or fresh leaves which worms intend to devour, are 
dragged into the mouths of their burrows to a depth of from one to 
three inches, and are then moistened with a secreted fluid.  It has 
been assumed that this fluid serves to hasten their decay; but a 
large number of leaves were twice pulled out of the burrows of 
worms and kept for many weeks in a very moist atmosphere under a 
bell-glass in my study; and the parts which had been moistened by 
the worms did not decay more quickly in any plain manner than the 
other parts.  When fresh leaves were given in the evening to worms 
kept in confinement and examined early on the next morning, 
therefore not many hours after they had been dragged into the 
burrows, the fluid with which they were moistened, when tested with 
neutral litmus paper, showed an alkaline reaction.  This was 
repeatedly found to be the case with celery, cabbage and turnip 
leaves.  Parts of the same leaves which had not been moistened by 
the worms, were pounded with a few drops of distilled water, and 
the juice thus extracted was not alkaline.  Some leaves, however, 
which had been drawn into burrows out of doors, at an unknown 
antecedent period, were tried, and though still moist, they rarely 
exhibited even a trace of alkaline reaction.

The fluid, with which the leaves are bathed, acts on them whilst 
they are fresh or nearly fresh, in a remarkable manner; for it 
quickly kills and discolours them.  Thus the ends of a fresh 
carrot-leaf, which had been dragged into a burrow, were found after 
twelve hours of a dark brown tint.  Leaves of celery, turnip, 
maple, elm, lime, thin leaves of ivy, and, occasionally those of 
the cabbage were similarly acted on.  The end of a leaf of Triticum 
repens, still attached to a growing plant, had been drawn into a 
burrow, and this part was dark brown and dead, whilst the rest of 
the leaf was fresh and green.  Several leaves of lime and elm 
removed from burrows out of doors were found affected in different 
degrees.  The first change appears to be that the veins become of a 
dull reddish-orange.  The cells with chlorophyll next lose more or 
less completely their green colour, and their contents finally 
become brown.  The parts thus affected often appeared almost black 
by reflected light; but when viewed as a transparent object under 
the microscope, minute specks of light were transmitted, and this 
was not the case with the unaffected parts of the same leaves.  
These effects, however, merely show that the secreted fluid is 
highly injurious or poisonous to leaves; for nearly the same 
effects were produced in from one to two days on various kinds of 
young leaves, not only by artificial pancreatic fluid, prepared 
with or without thymol, but quickly by a solution of thymol by 
itself.  On one occasion leaves of Corylus were much discoloured by 
being kept for eighteen hours in pancreatic fluid, without any 
thymol.  With young and tender leaves immersion in human saliva 
during rather warm weather, acted in the same manner as the 
pancreatic fluid, but not so quickly.  The leaves in all these 
cases often became infiltrated with the fluid.

Large leaves from an ivy plant growing on a wall were so tough that 
they could not be gnawed by worms, but after four days they were 
affected in a peculiar manner by the secretion poured out of their 
mouths.  The upper surfaces of the leaves, over which the worms had 
crawled, as was shown by the dirt left on them, were marked in 
sinuous lines, by either a continuous or broken chain of whitish 
and often star-shaped dots, about 2 mm. in diameter.  The 
appearance thus presented was curiously like that of a leaf, into 
which the larva of some minute insect had burrowed.  But my son 
Francis, after making and examining sections, could nowhere find 
that the cell-walls had been broken down or that the epidermis had 
been penetrated.  When the section passed through the whitish dots, 
the grains of chlorophyll were seen to be more or less discoloured, 
and some of the palisade and mesophyll cells contained nothing but 
broken down granular matter.  These effects must be attributed to 
the transudation of the secretion through the epidermis into the 
cells.

The secretion with which worms moisten leaves likewise acts on the 
starch-granules within the cells.  My son examined some leaves of 
the ash and many of the lime, which had fallen off the trees and 
had been partly dragged into worm-burrows.  It is known that with 
fallen leaves the starch-grains are preserved in the guard-cells of 
the stomata.  Now in several cases the starch had partially or 
wholly disappeared from these cells, in the parts which had been 
moistened by the secretion; while it was still well preserved in 
the other parts of the same leaves.  Sometimes the starch was 
dissolved out of only one of the two guard-cells.  The nucleus in 
one case had disappeared, together with the starch-granules.  The 
mere burying of lime-leaves in damp earth for nine days did not 
cause the destruction of the starch-granules.  On the other hand, 
the immersion of fresh lime and cherry leaves for eighteen hours in 
artificial pancreatic fluid, led to the dissolution of the starch-
granules in the guard-cells as well as in the other cells.

From the secretion with which the leaves are moistened being 
alkaline, and from its acting both on the starch-granules and on 
the protoplasmic contents of the cells, we may infer that it 
resembles in nature not saliva, {22} but pancreatic secretion; and 
we know from Fredericq that a secretion of this kind is found in 
the intestines of worms.  As the leaves which are dragged into the 
burrows are often dry and shrivelled, it is indispensable for their 
disintegration by the unarmed mouths of worms that they should 
first be moistened and softened; and fresh leaves, however soft and 
tender they may be, are similarly treated, probably from habit.  
The result is that they are partially digested before they are 
taken into the alimentary canal.  I am not aware of any other case 
of extra-stomachal digestion having been recorded.  The boa-
constrictor is said to bathe its prey with saliva, but this is 
doubtful; and it is done solely for the sake of lubricating its 
prey.  Perhaps the nearest analogy may be found in such plants as 
Drosera and Dionaea; for here animal matter is digested and 
converted into peptone not within a stomach, but on the surfaces of 
the leaves.

Calciferous Glands.--These glands (see Fig. 1), judging from their 
size and from their rich supply of blood-vessels, must be of much 
importance to the animal.  But almost as many theories have been 
advanced on their use as there have been observers.  They consist 
of three pairs, which in the common earth-worm debouch into the 
alimentary canal in advance of the gizzard, but posteriorly to it 
in Urochaeta and some other genera. {23}  The two posterior pairs 
are formed by lamellae, which, according to Claparede, are 
diverticula from the oesophagus. {24}  These lamellae are coated 
with a pulpy cellular layer, with the outer cells lying free in 
infinite numbers.  If one of these glands is punctured and 
squeezed, a quantity of white pulpy matter exudes, consisting of 
these free cells.  They are minute, and vary in diameter from 2 to 
6 microns.  They contain in their centres a little excessively fine 
granular matter; but they look so like oil globules that Claparede 
and others at first treated them with ether.  This produces no 
effect; but they are quickly dissolved with effervescence in acetic 
acid, and when oxalate of ammonia is added to the solution a white 
precipitate is thrown down.  We may therefore conclude that they 
contain carbonate of lime.  If the cells are immersed in a very 
little acid, they become more transparent, look like ghosts, and 
are soon lost to view; but if much acid is added, they disappear 
instantly.  After a very large number have been dissolved, a 
flocculent residue is left, which apparently consists of the 
delicate ruptured cell-walls.  In the two posterior pairs of glands 
the carbonate of lime contained in the cells occasionally 
aggregates into small rhombic crystals or into concretions, which 
lie between the lamellae; but I have seen only one case, and 
Claparede only a very few such cases.

The two anterior glands differ a little in shape from the four 
posterior ones, by being more oval.  They differ also conspicuously 
in generally containing several small, or two or three larger, or a 
single very large concretion of carbonate of lime, as much as 1.5 
mm. in diameter.  When a gland includes only a few very small 
concretions, or, as sometimes happens, none at all, it is easily 
overlooked.  The large concretions are round or oval, and 
exteriorly almost smooth.  One was found which filled up not only 
the whole gland, as is often the case, but its neck; so that it 
resembled an olive-oil flask in shape.  These concretions when 
broken are seen to be more or less crystalline in structure.  How 
they escape from the gland is a marvel; but that they do escape is 
certain, for they are often found in the gizzard, intestines, and 
in the castings of worms, both with those kept in confinement and 
those in a state of nature.

Claparede says very little about the structure of the two anterior 
glands, and he supposes that the calcareous matter of which the 
concretions are formed is derived from the four posterior glands.  
But if an anterior gland which contains only small concretions is 
placed in acetic acid and afterwards dissected, or if sections are 
made of such a gland without being treated with acid, lamellae like 
those in the posterior glands and coated with cellular matter could 
be plainly seen, together with a multitude of free calciferous 
cells readily soluble in acetic acid.  When a gland is completely 
filled with a single large concretion, there are no free cells, as 
these have been all consumed in forming the concretion.  But if 
such a concretion, or one of only moderately large size, is 
dissolved in acid, much membranous matter is left, which appears to 
consist of the remains of the formerly active lamellae.  After the 
formation and expulsion of a large concretion, new lamellae must be 
developed in some manner.  In one section made by my son, the 
process had apparently commenced, although the gland contained two 
rather large concretions, for near the walls several cylindrical 
and oval pipes were intersected, which were lined with cellular 
matter and were quite filled with free calciferous cells.  A great 
enlargement in one direction of several oval pipes would give rise 
to the lamellae.

Besides the free calciferous cells in which no nucleus was visible, 
other and rather larger free cells were seen on three occasions; 
and these contained a distinct nucleus and nucleolus.  They were 
only so far acted on by acetic acid that the nucleus was thus 
rendered more distinct.  A very small concretion was removed from 
between two of the lamellae within an anterior gland.  It was 
imbedded in pulpy cellular matter, with many free calciferous 
cells, together with a multitude of the larger, free, nucleated 
cells, and these latter cells were not acted on by acetic acid, 
while the former were dissolved.  From this and other such cases I 
am led to suspect that the calciferous cells are developed from the 
larger nucleated ones; but how this was effected was not 
ascertained.

When an anterior gland contains several minute concretions, some of 
these are generally angular or crystalline in outline, while the 
greater number are rounded with an irregular mulberry-like surface.  
Calciferous cells adhered to many parts of these mulberry-like 
masses, and their gradual disappearance could be traced while they 
still remained attached.  It was thus evident that the concretions 
are formed from the lime contained within the free calciferous 
cells.  As the smaller concretions increase in size, they come into 
contact and unite, thus enclosing the now functionless lamellae; 
and by such steps the formation of the largest concretions could be 
followed.  Why the process regularly takes place in the two 
anterior glands, and only rarely in the four posterior glands, is 
quite unknown.  Morren says that these glands disappear during the 
winter; and I have seen some instances of this fact, and others in 
which either the anterior or posterior glands were at this season 
so shrunk and empty, that they could be distinguished only with 
much difficulty.

With respect to the function of the calciferous glands, it is 
probable that they primarily serve as organs of excretion, and 
secondarily as an aid to digestion.  Worms consume many fallen 
leaves; and it is known that lime goes on accumulating in leaves 
until they drop off the parent-plant, instead of being re-absorbed 
into the stem or roots, like various other organic and inorganic 
substances. {25}  The ashes of a leaf of an acacia have been known 
to contain as much as 72 per cent. of lime.  Worms therefore would 
be liable to become charged with this earth, unless there were some 
special means for its excretion; and the calciferous glands are 
well adapted for this purpose.  The worms which live in mould close 
over the chalk, often have their intestines filled with this 
substance, and their castings are almost white.  Here it is evident 
that the supply of calcareous matter must be super-abundant.  
Nevertheless with several worms collected on such a site, the 
calciferous glands contained as many free calciferous cells, and 
fully as many and large concretions, as did the glands of worms 
which lived where there was little or no lime; and this indicates 
that the lime is an excretion, and not a secretion poured into the 
alimentary canal for some special purpose.

On the other hand, the following considerations render it highly 
probable that the carbonate of lime, which is excreted by the 
glands, aids the digestive process under ordinary circumstances.  
Leaves during their decay generate an abundance of various kinds of 
acids, which have been grouped together under the term of humus 
acids.  We shall have to recur to this subject in our fifth 
chapter, and I need here only say that these acids act strongly on 
carbonate of lime.  The half-decayed leaves which are swallowed in 
such large quantities by worms would, therefore, after they have 
been moistened and triturated in the alimentary canal, be apt to 
produce such acids.  And in the case of several worms, the contents 
of the alimentary canal were found to be plainly acid, as shown by 
litmus paper.  This acidity cannot be attributed to the nature of 
the digestive fluid, for pancreatic fluid is alkaline; and we have 
seen that the secretion which is poured out of the mouths of worms 
for the sake of preparing the leaves for consumption, is likewise 
alkaline.  The acidity can hardly be due to uric acid, as the 
contents of the upper part of the intestine were often acid.  In 
one case the contents of the gizzard were slightly acid, those of 
the upper intestines being more plainly acid.  In another case the 
contents of the pharynx were not acid, those of the gizzard 
doubtfully so, while those of the intestine were distinctly acid at 
a distance of 5 cm. below the gizzard.  Even with the higher 
herbivorous and omnivorous animals, the contents of the large 
intestine are acid.  "This, however, is not caused by any acid 
secretion from the mucous membrane; the reaction of the intestinal 
walls in the larger as in the small intestine is alkaline.  It must 
therefore arise from acid fermentations going on in the contents 
themselves . . .  In Carnivora the contents of the coecum are said 
to be alkaline, and naturally the amount of fermentation will 
depend largely on the nature of the food." {26}

With worms not only the contents of the intestines, but their 
ejected matter or the castings, are generally acid.  Thirty 
castings from different places were tested, and with three or four 
exceptions were found to be acid; and the exceptions may have been 
due to such castings not having been recently ejected; for some 
which were at first acid, were on the following morning, after 
being dried and again moistened, no longer acid; and this probably 
resulted from the humus acids being, as is known to be the case, 
easily decomposed.  Five fresh castings from worms which lived in 
mould close over the chalk, were of a whitish colour and abounded 
with calcareous matter; and these were not in the least acid.  This 
shows how effectually carbonate of lime neutralises the intestinal 
acids.  When worms were kept in pots filled with fine ferruginous 
sand, it was manifest that the oxide of iron, with which the grains 
of silex were coated, had been dissolved and removed from them in 
the castings.

The digestive fluid of worms resembles in its action, as already 
stated, the pancreatic secretion of the higher animals; and in 
these latter, "pancreatic digestion is essentially alkaline; the 
action will not take place unless some alkali be present; and the 
activity of an alkaline juice is arrested by acidification, and 
hindered by neutralization." {27}  Therefore it seems highly 
probable that the innumerable calciferous cells, which are poured 
from the four posterior glands into the alimentary canal of worms, 
serve to neutralise more or less completely the acids there 
generated by the half-decayed leaves.  We have seen that these 
cells are instantly dissolved by a small quantity of acetic acid, 
and as they do not always suffice to neutralise the contents of 
even the upper part of the alimentary canal, the lime is perhaps 
aggregated into concretions in the anterior pair of glands, in 
order that some may be carried down to the posterior parts of the 
intestine, where these concretions would be rolled about amongst 
the acid contents.  The concretions found in the intestines and in 
the castings often have a worn appearance, but whether this is due 
to some amount of attrition or of chemical corrosion could not be 
told.  Claparede believes that they are formed for the sake of 
acting as mill-stones, and of thus aiding in the trituration of the 
food.  They may give some aid in this way; but I fully agree with 
Perrier that this must be of quite subordinate importance, seeing 
that the object is already attained by stones being generally 
present in the gizzards and intestines of worms.



CHAPTER II--HABITS OF WORMS--continued.



Manner in which worms seize objects--Their power of suction--The 
instinct of plugging up the mouths of their burrows--Stones piled 
over the burrows--The advantages thus gained--Intelligence shown by 
worms in their manner of plugging up their burrows--Various kinds 
of leaves and other objects thus used--Triangles of paper--Summary 
of reasons for believing that worms exhibit some intelligence--
Means by which they excavate their burrows, by pushing away the 
earth and swallowing it--Earth also swallowed for the nutritious 
matter which it contains--Depth to which worms burrow, and the 
construction of their burrows--Burrows lined with castings, and in 
the upper part with leaves--The lowest part paved with little 
stones or seeds--Manner in which the castings are ejected--The 
collapse of old burrows--Distribution of worms--Tower-like castings 
in Bengal--Gigantic castings on the Nilgiri Mountains--Castings 
ejected in all countries.


In the pots in which worms were kept, leaves were pinned down to 
the soil, and at night the manner in which they were seized could 
be observed.  The worms always endeavoured to drag the leaves 
towards their burrows; and they tore or sucked off small fragments, 
whenever the leaves were sufficiently tender.  They generally 
seized the thin edge of a leaf with their mouths, between the 
projecting upper and lower lip; the thick and strong pharynx being 
at the same time, as Perrier remarks, pushed forward within their 
bodies, so as to afford a point of resistance for the upper lip.  
In the case of broad flat objects they acted in a wholly different 
manner.  The pointed anterior extremity of the body, after being 
brought into contact with an object of this kind, was drawn within 
the adjoining rings, so that it appeared truncated and became as 
thick as the rest of the body.  This part could then be seen to 
swell a little; and this, I believe, is due to the pharynx being 
pushed a little forwards.  Then by a slight withdrawal of the 
pharynx or by its expansion, a vacuum was produced beneath the 
truncated slimy end of the body whilst in contact with the object; 
and by this means the two adhered firmly together. {28}  That under 
these circumstances a vacuum was produced was plainly seen on one 
occasion, when a large worm lying beneath a flaccid cabbage leaf 
tried to drag it away; for the surface of the leaf directly over 
the end of the worm's body became deeply pitted.  On another 
occasion a worm suddenly lost its hold on a flat leaf; and the 
anterior end of the body was momentarily seen to be cup-formed.  
Worms can attach themselves to an object beneath water in the same 
manner; and I saw one thus dragging away a submerged slice of an 
onion-bulb.

The edges of fresh or nearly fresh leaves affixed to the ground 
were often nibbled by the worms; and sometimes the epidermis and 
all the parenchyma on one side was gnawed completely away over a 
considerable space; the epidermis alone on the opposite side being 
left quite clean.  The veins were never touched, and leaves were 
thus sometimes partly converted into skeletons.  As worms have no 
teeth and as their mouths consist of very soft tissue, it may be 
presumed that they consume by means of suction the edges and the 
parenchyma of fresh leaves, after they have been softened by the 
digestive fluid.  They cannot attack such strong leaves as those of 
sea-kale or large and thick leaves of ivy; though one of the latter 
after it had become rotten was reduced in parts to the state of a 
skeleton.

Worms seize leaves and other objects, not only to serve as food, 
but for plugging up the mouths of their burrows; and this is one of 
their strongest instincts.  They sometimes work so energetically 
that Mr. D. F. Simpson, who has a small walled garden where worms 
abound in Bayswater, informs me that on a calm damp evening he 
there heard so extraordinary a rustling noise from under a tree 
from which many leaves had fallen, that he went out with a light 
and discovered that the noise was caused by many worms dragging the 
dry leaves and squeezing them into the burrows.  Not only leaves, 
but petioles of many kinds, some flower-peduncles, often decayed 
twigs of trees, bits of paper, feathers, tufts of wool and horse-
hairs are dragged into their burrows for this purpose.  I have seen 
as many as seventeen petioles of a Clematis projecting from the 
mouth of one burrow, and ten from the mouth of another.  Some of 
these objects, such as the petioles just named, feathers, &c., are 
never gnawed by worms.  In a gravel-walk in my garden I found many 
hundred leaves of a pine-tree (P. austriaca or nigricans) drawn by 
their bases into burrows.  The surfaces by which these leaves are 
articulated to the branches are shaped in as peculiar a manner as 
is the joint between the leg-bones of a quadruped; and if these 
surfaces had been in the least gnawed, the fact would have been 
immediately visible, but there was no trace of gnawing.  Of 
ordinary dicotyledonous leaves, all those which are dragged into 
burrows are not gnawed.  I have seen as many as nine leaves of the 
lime-tree drawn into the same burrow, and not nearly all of them 
had been gnawed; but such leaves may serve as a store for future 
consumption.  Where fallen leaves are abundant, many more are 
sometimes collected over the mouth of a burrow than can be used, so 
that a small pile of unused leaves is left like a roof over those 
which have been partly dragged in.

A leaf in being dragged a little way into a cylindrical burrow is 
necessarily much folded or crumpled.  When another leaf is drawn 
in, this is done exteriorly to the first one, and so on with the 
succeeding leaves; and finally all become closely folded and 
pressed together.  Sometimes the worm enlarges the mouth of its 
burrow, or makes a fresh one close by, so as to draw in a still 
larger number of leaves.  They often or generally fill up the 
interstices between the drawn-in leaves with moist viscid earth 
ejected from their bodies; and thus the mouths of the burrows are 
securely plugged.  Hundreds of such plugged burrows may be seen in 
many places, especially during the autumnal and early winter 
months.  But, as will hereafter be shown, leaves are dragged into 
the burrows not only for plugging them up and for food, but for the 
sake of lining the upper part or mouth.

When worms cannot obtain leaves, petioles, sticks, &c., with which 
to plug up the mouths of their burrows, they often protect them by 
little heaps of stones; and such heaps of smooth rounded pebbles 
may frequently be seen on gravel-walks.  Here there can be no 
question about food.  A lady, who was interested in the habits of 
worms, removed the little heaps of stones from the mouths of 
several burrows and cleared the surface of the ground for some 
inches all round.  She went out on the following night with a 
lantern, and saw the worms with their tails fixed in their burrows, 
dragging the stones inwards by the aid of their mouths, no doubt by 
suction.  "After two nights some of the holes had 8 or 9 small 
stones over them; after four nights one had about 30, and another 
34 stones." {29}  One stone--which had been dragged over the 
gravel-walk to the mouth of a burrow weighed two ounces; and this 
proves how strong worms are.  But they show greater strength in 
sometimes displacing stones in a well-trodden gravel-walk; that 
they do so, may be inferred from the cavities left by the displaced 
stones being exactly filled by those lying over the mouths of 
adjoining burrows, as I have myself observed.

Work of this kind is usually performed during the night; but I have 
occasionally known objects to be drawn into the burrows during the 
day.  What advantage the worms derive from plugging up the mouths 
of their burrows with leaves, &c., or from piling stones over them, 
is doubtful.  They do not act in this manner at the times when they 
eject much earth from their burrows; for their castings then serve 
to cover the mouths.  When gardeners wish to kill worms on a lawn, 
it is necessary first to brush or rake away the castings from the 
surface, in order that the lime-water may enter the burrows. {30}  
It might be inferred from this fact that the mouths are plugged up 
with leaves, &c., to prevent the entrance of water during heavy 
rain; but it may be urged against this view that a few, loose, 
well-rounded stones are ill-adapted to keep out water.  I have 
moreover seen many burrows in the perpendicularly cut turf-edgings 
to gravel-walks, into which water could hardly flow, as well 
plugged as burrows on a level surface.  It is not probable that the 
plugs or piles of stones serve to conceal the burrows from 
scolopendras, which, according to Hoffmeister, {31} are the 
bitterest enemies of worms, or from the larger species of Carabus 
and Staphylinus which attack them ferociously, for these animals 
are nocturnal, and the burrows are opened at night.  May not worms 
when the mouth of the burrow is protected be able to remain with 
safety with their heads close to it, which we know that they like 
to do, but which costs so many of them their lives?  Or may not the 
plugs check the free ingress of the lowest stratum of air, when 
chilled by radiation at night, from the surrounding ground and 
herbage?  I am inclined to believe in this latter view:  firstly, 
because when worms were kept in pots in a room with a fire, in 
which case cold air could not enter the burrows, they plugged them 
up in a slovenly manner; and secondarily, because they often coat 
the upper part of their burrows with leaves, apparently to prevent 
their bodies from coming into close contact with the cold damp 
earth.  Mr. E. Parfitt has suggested to me that the mouths of the 
burrows are closed in order that the air within them may be kept 
thoroughly damp, and this seems the most probable explanation of 
the habit.  But the plugging-up process may serve for all the above 
purposes.

Whatever the motive may be, it appears that worms much dislike 
leaving the mouths of their burrows open.  Nevertheless they will 
reopen them at night, whether or not they can afterwards close 
them.  Numerous open burrows may be seen on recently-dug ground, 
for in this case the worms eject their castings in cavities left in 
the ground, or in the old burrows instead of piling them over the 
mouths of their burrows, and they cannot collect objects on the 
surface by which the mouths might be protected.  So again on a 
recently disinterred pavement of a Roman villa at Abinger 
(hereafter to be described) the worms pertinaciously opened their 
burrows almost every night, when these had been closed by being 
trampled on, although they were rarely able to find a few minute 
stones wherewith to protect them.

Intelligence shown by worms in their manner of plugging up their 
burrows.--If a man had to plug up a small cylindrical hole, with 
such objects as leaves, petioles or twigs, he would drag or push 
them in by their pointed ends; but if these objects were very thin 
relatively to the size of the hole, he would probably insert some 
by their thicker or broader ends.  The guide in his case would be 
intelligence.  It seemed therefore worth while to observe carefully 
how worms dragged leaves into their burrows; whether by their tips 
or bases or middle parts.  It seemed more especially desirable to 
do this in the case of plants not natives to our country; for 
although the habit of dragging leaves into their burrows is 
undoubtedly instinctive with worms, yet instinct could not tell 
them how to act in the case of leaves about which their progenitors 
knew nothing.  If, moreover, worms acted solely through instinct or 
an unvarying inherited impulse, they would draw all kinds of leaves 
into their burrows in the same manner.  If they have no such 
definite instinct, we might expect that chance would determine 
whether the tip, base or middle was seized.  If both these 
alternatives are excluded, intelligence alone is left; unless the 
worm in each case first tries many different methods, and follows 
that alone which proves possible or the most easy; but to act in 
this manner and to try different methods makes a near approach to 
intelligence.

In the first place 227 withered leaves of various kinds, mostly of 
English plants, were pulled out of worm-burrows in several places.  
Of these, 181 had been drawn into the burrows by or near their 
tips, so that the foot-stalk projected nearly upright from the 
mouth of the burrow; 20 had been drawn in by their bases, and in 
this case the tips projected from the burrows; and 26 had been 
seized near the middle, so that these had been drawn in 
transversely and were much crumpled.  Therefore 80 per cent. 
(always using the nearest whole number) had been drawn in by the 
tip, 9 per cent. by the base or foot-stalk, and 11 per cent. 
transversely or by the middle.  This alone is almost sufficient to 
show that chance does not determine the manner in which leaves are 
dragged into the burrows.

Of the above 227 leaves, 70 consisted of the fallen leaves of the 
common lime-tree, which is almost certainly not a native of 
England.  These leaves are much acuminated towards the tip, and are 
very broad at the base with a well-developed foot-stalk.  They are 
thin and quite flexible when half-withered.  Of the 70, 79 per 
cent. had been drawn in by or near the tip; 4 per cent. by or near 
the base; and 17 per cent. transversely or by the middle.  These 
proportions agree very closely, as far as the tip is concerned, 
with those before given.  But the percentage drawn in by the base 
is smaller, which may be attributed to the breadth of the basal 
part of the blade.  We here, also, see that the presence of a foot-
stalk, which it might have been expected would have tempted the 
worms as a convenient handle, has little or no influence in 
determining the manner in which lime leaves are dragged into the 
burrows.  The considerable proportion, viz., 17 per cent., drawn in 
more or less transversely depends no doubt on the flexibility of 
these half-decayed leaves.  The fact of so many having been drawn 
in by the middle, and of some few having been drawn in by the base, 
renders it improbable that the worms first tried to draw in most of 
the leaves by one or both of these methods, and that they 
afterwards drew in 79 per cent. by their tips; for it is clear that 
they would not have failed in drawing them in by the base or 
middle.

The leaves of a foreign plant were next searched for, the blades of 
which were not more pointed towards the apex than towards the base.  
This proved to be the case with those of a laburnum (a hybrid 
between Cytisus alpinus and laburnum) for on doubling the terminal 
over the basal half, they generally fitted exactly; and when there 
was any difference, the basal half was a little the narrower.  It 
might, therefore, have been expected that an almost equal number of 
these leaves would have been drawn in by the tip and base, or a 
slight excess in favour of the latter.  But of 73 leaves (not 
included in the first lot of 227) pulled out of worm-burrows, 63 
per cent. had been drawn in by the tip; 27 per cent. by the base, 
and 10 per cent. transversely.  We here see that a far larger 
proportion, viz., 27 per cent. were drawn in by the base than in 
the case of lime leaves, the blades of which are very broad at the 
base, and of which only 4 per cent. had thus been drawn in.  We may 
perhaps account for the fact of a still larger proportion of the 
laburnum leaves not having been drawn in by the base, by worms 
having acquired the habit of generally drawing in leaves by their 
tips and thus avoiding the foot-stalk.  For the basal margin of the 
blade in many kinds of leaves forms a large angle with the foot-
stalk; and if such a leaf were drawn in by the foot-stalk, the 
basal margin would come abruptly into contact with the ground on 
each side of the burrow, and would render the drawing in of the 
leaf very difficult.

Nevertheless worms break through their habit of avoiding the foot-
stalk, if this part offers them the most convenient means for 
drawing leaves into their burrows.  The leaves of the endless 
hybridised varieties of the Rhododendron vary much in shape; some 
are narrowest towards the base and others towards the apex.  After 
they have fallen off, the blade on each side of the midrib often 
becomes curled up while drying, sometimes along the whole length, 
sometimes chiefly at the base, sometimes towards the apex.  Out of 
28 fallen leaves on one bed of peat in my garden, no less than 23 
were narrower in the basal quarter than in the terminal quarter of 
their length; and this narrowness was chiefly due to the curling in 
of the margins.  Out of 36 fallen leaves on another bed, in which 
different varieties of the Rhododendron grew, only 17 were narrower 
towards the base than towards the apex.  My son William, who first 
called my attention to this case, picked up 237 fallen leaves in 
his garden (where the Rhododendron grows in the natural soil) and 
of these 65 per cent. could have been drawn by worms into their 
burrows more easily by the base or foot-stalk than by the tip; and 
this was partly due to the shape of the leaf and in a less degree 
to the curling in of the margins:  27 per cent. could have been 
drawn in more easily by the tip than by the base:  and 8 per cent. 
with about equal ease by either end.  The shape of a fallen leaf 
ought to be judged of before one end has been drawn into a burrow, 
for after this has happened, the free end, whether it be the base 
or apex, will dry more quickly than the end imbedded in the damp 
ground; and the exposed margins of the free end will consequently 
tend to become more curled inwards than they were when the leaf was 
first seized by the worm.  My son found 91 leaves which had been 
dragged by worms into their burrows, though not to a great depth; 
of these 66 per cent. had been drawn in by the base or foot-stalk; 
and 34 per cent, by the tip.  In this case, therefore, the worms 
judged with a considerable degree of correctness how best to draw 
the withered leaves of this foreign plant into their burrows; 
notwithstanding that they had to depart from their usual habit of 
avoiding the foot-stalk.

On the gravel-walks in my garden a very large number of leaves of 
three species of Pinus (P. austriaca, nigricans and sylvestris) are 
regularly drawn into the mouths of worm burrows.  These leaves 
consist of two so-called needles, which are of considerable length 
in the two first and short in the last named species, and are 
united to a common base; and it is by this part that they are 
almost invariably drawn into the burrows.  I have seen only two or 
at most three exceptions to this rule with worms in a state of 
nature.  As the sharply pointed needles diverge a little, and as 
several leaves are drawn into the same burrow, each tuft forms a 
perfect chevaux de frise.  On two occasions many of these tufts 
were pulled up in the evening, but by the following morning fresh 
leaves had been pulled in, and the burrows were again well 
protected.  These leaves could not be dragged into the burrows to 
any depth, except by their bases, as a worm cannot seize hold of 
the two needles at the same time, and if one alone were seized by 
the apex, the other would be pressed against the ground and would 
resist the entry of the seized one.  This was manifest in the above 
mentioned two or three exceptional cases.  In order, therefore, 
that worms should do their work well, they must drag pine-leaves 
into their burrows by their bases, where the two needles are 
conjoined.  But how they are guided in this work is a perplexing 
question.

This difficulty led my son Francis and myself to observe worms in 
confinement during several nights by the aid of a dim light, while 
they dragged the leaves of the above named pines into their 
burrows.  They moved the anterior extremities of their bodies about 
the leaves, and on several occasions when they touched the sharp 
end of a needle they withdrew suddenly as if pricked.  But I doubt 
whether they were hurt, for they are indifferent to very sharp 
objects, and will swallow even rose-thorns and small splinters of 
glass.  It may also be doubted, whether the sharp ends of the 
needles serve to tell them that this is the wrong end to seize; for 
the points were cut off many leaves for a length of about one inch, 
and fifty-seven of them thus treated were drawn into the burrows by 
their bases, and not one by the cut-off ends.  The worms in 
confinement often seized the needles near the middle and drew them 
towards the mouths of their burrows; and one worm tried in a 
senseless manner to drag them into the burrow by bending them.  
They sometimes collected many more leaves over the mouths of their 
burrows (as in the case formerly mentioned of lime-leaves) than 
could enter them.  On other occasions, however, they behaved very 
differently; for as soon as they touched the base of a pine-leaf, 
this was seized, being sometimes completely engulfed in their 
mouths, or a point very near the base was seized, and the leaf was 
then quickly dragged or rather jerked into their burrows.  It 
appeared both to my son and myself as if the worms instantly 
perceived as soon as they had seized a leaf in the proper manner.  
Nine such cases were observed, but in one of them the worm failed 
to drag the leaf into its burrow, as it was entangled by other 
leaves lying near.  In another case a leaf stood nearly upright 
with the points of the needles partly inserted into a burrow, but 
how placed there was not seen; and then the worm reared itself up 
and seized the base, which was dragged into the mouth of the burrow 
by bowing the whole leaf.  On the other hand, after a worm had 
seized the base of a leaf, this was on two occasions relinquished 
from some unknown motive.

As already remarked, the habit of plugging up the mouths of the 
burrows with various objects, is no doubt instinctive in worms; and 
a very young one, born in one of my pots, dragged for some little 
distance a Scotch-fir leaf, one needle of which was as long and 
almost as thick as its own body.  No species of pine is endemic in 
this part of England, it is therefore incredible that the proper 
manner of dragging pine-leaves into the burrows can be instinctive 
with our worms.  But as the worms on which the above observations 
were made, were dug up beneath or near some pines, which had been 
planted there about forty years, it was desirable to prove that 
their actions were not instinctive.  Accordingly, pine-leaves were 
scattered on the ground in places far removed from any pine-tree, 
and 90 of them were drawn into the burrows by their bases.  Only 
two were drawn in by the tips of the needles, and these were not 
real exceptions, as one was drawn in for a very short distance, and 
the two needles of the other cohered.  Other pine-leaves were given 
to worms kept in pots in a warm room, and here the result was 
different; for out of 42 leaves drawn into the burrows, no less 
than i6 were drawn in by the tips of the needles.  These worms, 
however, worked in a careless or slovenly manner; for the leaves 
were often drawn in to only a small depth; sometimes they were 
merely heaped over the mouths of the burrows, and sometimes none 
were drawn in.  I believe that this carelessness may be accounted 
for either by the warmth of the air, or by its dampness, as the 
pots were covered by glass plates; the worms consequently did not 
care about plugging up their holes effectually.  Pots tenanted by 
worms and covered with a net which allowed the free entrance of 
air, were left out of doors for several nights, and now 72 leaves 
were all properly drawn in by their bases.

It might perhaps be inferred from the facts as yet given, that 
worms somehow gain a general notion of the shape or structure of 
pine-leaves, and perceive that it is necessary for them to seize 
the base where the two needles are conjoined.  But the following 
cases make this more than doubtful.  The tips of a large number of 
needles of P. austriaca were cemented together with shell-lac 
dissolved in alcohol, and were kept for some days, until, as I 
believe, all odour or taste had been lost; and they were then 
scattered on the ground where no pine-trees grew, near burrows from 
which the plugging had been removed.  Such leaves could have been 
drawn into the burrows with equal ease by either end; and judging 
from analogy and more especially from the case presently to be 
given of the petioles of Clematis montana, I expected that the apex 
would have been preferred.  But the result was that out of 121 
leaves with the tips cemented, which were drawn into burrows, 108 
were drawn in by their bases, and only 13 by their tips.  Thinking 
that the worms might possibly perceive and dislike the smell or 
taste of the shell-lac, though this was very improbable, especially 
after the leaves had been left out during several nights, the tips 
of the needles of many leaves were tied together with fine thread.  
Of leaves thus treated 150 were drawn into burrows--123 by the base 
and 27 by the tied tips; so that between four land five times as 
many were drawn in by the base as by the tip.  It is possible that 
the short cut-off ends of the thread with which they were tied, may 
have tempted the worms to drag in a larger proportional number by 
the tips than when cement was used.  Of the leaves with tied and 
cemented tips taken together (271 in number) 85 per cent. were 
drawn in by the base and 15 per cent. by the tips.  We may 
therefore infer that it is not the divergence of the two needles 
which leads worms in a state of nature almost invariably to drag 
pine-leaves into their burrows by the base.  Nor can it be the 
sharpness of the points of the needles which determines them; for, 
as we have seen, many leaves with the points cut off were drawn in 
by their bases.  We are thus led to conclude, that with pine-leaves 
there must be something attractive to worms in the base, 
notwithstanding that few ordinary leaves are drawn in by the base 
or foot-stalk.

Petioles.--We will now turn to the petioles or foot-stalks of 
compound leaves, after the leaflets have fallen off.  Those from 
Clematis montana, which grew over a verandah, were dragged early in 
January in large numbers into the burrows on an adjoining gravel-
walk, lawn, and flower-bed.  These petioles vary from 2.5 to 4.5 
inches in length, are rigid and of nearly uniform thickness, except 
close to the base where they thicken rather abruptly, being here 
about twice as thick as in any other part.  The apex is somewhat 
pointed, but soon withers and is then easily broken off.  Of these 
petioles, 314 were pulled out of burrows in the above specified 
sites; and it was found that 76 per cent. had been drawn in by 
their tips, and 24 per cent by their bases; so that those drawn in 
by the tip were a little more than thrice as many as those drawn in 
by the base.  Some of those extracted from the well-beaten gravel-
walk were kept separate from the others; and of these (59 in 
number) nearly five times as many had been drawn in by the tip as 
by the base; whereas of those extracted from the lawn and flower-
bed, where from the soil yielding more easily, less care would be 
necessary in plugging up the burrows, the proportion of those drawn 
in by the tip (130) to those drawn in by the base (48) was rather 
less than three to one.  That these petioles had been dragged into 
the burrows for plugging them up, and not for food, was manifest, 
as neither end, as far as I could see, had been gnawed.  As several 
petioles are used to plug up the same burrow, in one case as many 
as 10, and in another case as many as 15, the worms may perhaps at 
first draw in a few by the thicker end so as to save labour; but 
afterwards a large majority are drawn in by the pointed end, in 
order to plug up the hole securely.

The fallen petioles of our native ash-tree were next observed, and 
the rule with most objects, viz., that a large majority are dragged 
into the burrows by the more pointed end, had not here been 
followed; and this fact much surprised me at first.  These petioles 
vary in length from 5 to 8.5 inches; they are thick and fleshy 
towards the base, whence they taper gently towards the apex, which 
is a little enlarged and truncated where the terminal leaflet had 
been originally attached.  Under some ash-trees growing in a grass-
field, 229 petioles were pulled out of worm burrows early in 
January, and of these 51.5 per cent. had been drawn in by the base, 
and 48.5 per cent. by the apex.  This anomaly was however readily 
explained as soon as the thick basal part was examined; for in 78 
out of 103 petioles, this part had been gnawed by worms, just above 
the horse-shoe shaped articulation.  In most cases there could be 
no mistake about the gnawing; for ungnawed petioles which were 
examined after being exposed to the weather for eight additional 
weeks had not become more disintegrated or decayed near the base 
than elsewhere.  It is thus evident that the thick basal end of the 
petiole is drawn in not solely for the sake of plugging up the 
mouths of the burrows, but as food.  Even the narrow truncated tips 
of some few petioles had been gnawed; and this was the case in 6 
out of 37 which were examined for this purpose.  Worms, after 
having drawn in and gnawed the basal end, often push the petioles 
out of their burrows; and then drag in fresh ones, either by the 
base for food, or by the apex for plugging up the mouth more 
effectually.  Thus, out of 37 petioles inserted by their tips, 5 
had been previously drawn in by the base, for this part had been 
gnawed.  Again, I collected a handful of petioles lying loose on 
the ground close to some plugged-up burrows, where the surface was 
thickly strewed with other petioles which apparently had never been 
touched by worms; and 14 out of 47 (i.e. nearly one-third), after 
having had their bases gnawed had been pushed out of the burrows 
and were now lying on the ground.  From these several facts we may 
conclude that worms draw in some petioles of the ash by the base to 
serve as food, and others by the tip to plug up the mouths of their 
burrows in the most efficient manner.

The petioles of Robinia pseudo-acacia vary from 4 or 5 to nearly 12 
inches in length; they are thick close to the base before the 
softer parts have rotted off, and taper much towards the upper end.  
They are so flexible that I have seen some few doubled up and thus 
drawn into the burrows of worms.  Unfortunately these petioles were 
not examined until February, by which time the softer parts had 
completely rotted off, so that it was impossible to ascertain 
whether worms had gnawed the bases, though this is in itself 
probable.  Out of 121 petioles extracted from burrows early in 
February, 68 were imbedded by the base, and 53 by the apex.  On 
February 5 all the petioles which had been drawn into the burrows 
beneath a Robinia, were pulled up; and after an interval of eleven 
days, 35 petioles had been again dragged in, 19 by the base, and 16 
by the apex.  Taking these two lots together, 56 per cent. were 
drawn in by the base, and 44 per cent. by the apex.  As all the 
softer parts had long ago rotted off, we may feel sure, especially 
in the latter case, that none had been drawn in as food.  At this 
season, therefore, worms drag these petioles into their burrows 
indifferently by either end, a slight preference being given to the 
base.  This latter fact may be accounted for by the difficulty of 
plugging up a burrow with objects so extremely thin as are the 
upper ends.  In support of this view, it may be stated that out of 
the 16 petioles which had been drawn in by their upper ends, the 
more attenuated terminal portion of 7 had been previously broken 
off by some accident.

Triangles of paper.--Elongated triangles were cut out of moderately 
stiff writing-paper, which was rubbed with raw fat on both sides, 
so as to prevent their becoming excessively limp when exposed at 
night to rain and dew.  The sides of all the triangles were three 
inches in length, with the bases of 120 one inch, and of the other 
183 half an inch in length.  These latter triangles were very 
narrow or much acuminated. {32}  As a check on the observations 
presently to be given, similar triangles in a damp state were 
seized by a very narrow pair of pincers at different points and at 
all inclinations with reference to the margins, and were then drawn 
into a short tube of the diameter of a worm-burrow.  If seized by 
the apex, the triangle was drawn straight into the tube, with its 
margins infolded; if seized at some little distance from the apex, 
for instance at half an inch, this much was doubled back within the 
tube.  So it was with the base and basal angles, though in this 
case the triangles offered, as might have been expected, much more 
resistance to being drawn in.  If seized near the middle the 
triangle was doubled up, with the apex and base left sticking out 
of the tube.  As the sides of the triangles were three inches in 
length, the result of their being drawn into a tube or into a 
burrow in different ways, may be conveniently divided into three 
groups:  those drawn in by the apex or within an inch of it; those 
drawn in by the base or within an inch of it; and those drawn in by 
any point in the middle inch.

In order to see how the triangles would be seized by worms, some in 
a damp state were given to worms kept in confinement.  They were 
seized in three different manners in the case of both the narrow 
and broad triangles:  viz., by the margin; by one of the three 
angles, which was often completely engulfed in their mouths; and 
lastly, by suction applied to any part of the flat surface.  If 
lines parallel to the base and an inch apart, are drawn across a 
triangle with the sides three inches in length, it will be divided 
into three parts of equal length.  Now if worms seized 
indifferently by chance any part, they would assuredly seize on the 
basal part or division far oftener than on either of the two other 
divisions.  For the area of the basal to the apical part is as 5 to 
1, so that the chance of the former being drawn into a burrow by 
suction, will be as 5 to 1, compared with the apical part.  The 
base offers two angles and the apex only one, so that the former 
would have twice as good a chance (independently of the size of the 
angles) of being engulfed in a worm's mouth, as would the apex.  It 
should, however, be stated that the apical angle is not often 
seized by worms; the margin at a little distance on either side 
being preferred.  I judge of this from having found in 40 out of 46 
cases in which triangles had been drawn into burrows by their 
apical ends, that the tip had been doubled back within the burrow 
for a length of between 1/20 of an inch and 1 inch.  Lastly, the 
proportion between the margins of the basal and apical parts is as 
3 to 2 for the broad, and 2.5 to 2 for the narrow triangles.  From 
these several considerations it might certainly have been expected, 
supposing that worms seized hold of the triangles by chance, that a 
considerably larger proportion would have been dragged into the 
burrows by the basal than by the apical part; but we shall 
immediately see how different was the result.

Triangles of the above specified sizes were scattered on the ground 
in many places and on many successive nights near worm-burrows, 
from which the leaves, petioles, twigs, &c., with which they had 
been plugged, were removed.  Altogether 303 triangles were drawn by 
worms into their burrows:  12 others were drawn in by both ends, 
but as it was impossible to judge by which end they had been first 
seized, these are excluded.  Of the 303, 62 per cent. had been 
drawn in by the apex (using this term for all drawn in by the 
apical part, one inch in length); 15 per cent. by the middle; and 
23 per cent. by the basal part.  If they had been drawn 
indifferently by any point, the proportion for the apical, middle 
and basal parts would have been 33.3 per cent. for each; but, as we 
have just seen, it might have been expected that a much larger 
proportion would have been drawn in by the basal than by any other 
part.  As the case stands, nearly three times as many were drawn in 
by the apex as by the base.  If we consider the broad triangles by 
themselves, 59 per cent. were drawn in by the apex, 25 per cent. by 
the middle, and 16 per cent. by the base.  Of the narrow triangles, 
65 per cent. were drawn in by the apex, 14 per cent, by the middle, 
and 21 per cent. by the base; so that here those drawn in by the 
apex were more than 3 times as many as those drawn in by the base.  
We may therefore conclude that the manner in which the triangles 
are drawn into the burrows is not a matter of chance.

In eight cases, two triangles had been drawn into the same burrow, 
and in seven of these cases, one had been drawn in by the apex and 
the other by the base.  This again indicates that the result is not 
determined by chance.  Worms appear sometimes to revolve in the act 
of drawing in the triangles, for five out of the whole lot had been 
wound into an irregular spire round the inside of the burrow.  
Worms kept in a warm room drew 63 triangles into their burrows; 
but, as in the case of the pine-leaves, they worked in a rather 
careless manner, for only 44 per cent. were drawn in by the apex, 
22 per cent. by the middle, and 33 per cent. by the base.  In five 
cases, two triangles were drawn into the same burrow.

It may be suggested with much apparent probability that so large a 
proportion of the triangles were drawn in by the apex, not from the 
worms having selected this end as the most convenient for the 
purpose, but from having first tried in other ways and failed.  
This notion was countenanced by the manner in which worms in 
confinement were seen to drag about and drop the triangles; but 
then they were working carelessly.  I did not at first perceive the 
importance of this subject, but merely noticed that the bases of 
those triangles which had been drawn in by the apex, were generally 
clean and not crumpled.  The subject was afterwards attended to 
carefully.  In the first place several triangles which had been 
drawn in by the basal angles, or by the base, or a little above the 
base, and which were thus much crumpled and dirtied, were left for 
some hours in water and were then well shaken while immersed; but 
neither the dirt nor the creases were thus removed.  Only slight 
creases could be obliterated, even by pulling the wet triangles 
several times through my fingers.  Owing to the slime from the 
worms' bodies, the dirt was not easily washed off.  We may 
therefore conclude that if a triangle, before being dragged in by 
the apex, had been dragged into a burrow by its base with even a 
slight degree of force, the basal part would long retain its 
creases and remain dirty.  The condition of 89 triangles (65 narrow 
and 24 broad ones), which had been drawn in by the apex, was 
observed; and the bases of only 7 of them were at all creased, 
being at the same time generally dirty.  Of the 82 uncreased 
triangles, 14 were dirty at the base; but it does not follow from 
this fact that these had first been dragged towards the burrows by 
their bases; for the worms sometimes covered large portions of the 
triangles with slime, and these when dragged by the apex over the 
ground would be dirtied; and during rainy weather, the triangles 
were often dirtied over one whole side or over both sides.  If the 
worms had dragged the triangles to the mouths of their burrows by 
their bases, as often as by their apices, and had then perceived, 
without actually trying to draw them into the burrow, that the 
broader end was not well adapted for this purpose--even in this 
case a large proportion would probably have had their basal ends 
dirtied.  We may therefore infer--improbable as is the inference--
that worms are able by some means to judge which is the best end by 
which to draw triangles of paper into their burrows.

The percentage results of the foregoing observations on the manner 
in which worms draw various kinds of objects into the mouths of 
their burrows may be abridged as follows:-


                             Drawn
                             into the    Drawn in, Drawn in,
Nature of Object.            burrows,    by or     by or
                             by or       near      near
                             near the    the       the
                             apex.       middle.   base.
Leaves of various kinds          80        11         9
- of the Lime, basal margin
  of blade broad, apex
  acuminated                     79        17         4
- of a Laburnum, basal part of
  blade as narrow as, or some-
  times little narrower than
  the apical part                63        10        27
- of the Rhododendron, basal
  part of blade often narrower
  than the apical part           34       ...        66
- of Pine-trees, consisting of
  two needles arising from a
  common base                    ...      ...       100
Petioles of a Clematis,
  somewhat pointed at the apex,
  and blunt at the base          76       ...        24
- of the Ash, the thick basal
  end often drawn in to serve
  as food                       48.5      ...      51.5
- of Robinia, extremely thin,
  especially towards the apex,
  so as to be ill-fitted for
  plugging up the burrows        44      ...        56
Triangles of paper, of the
  two sizes                      62       15        23
- of the broad ones alone        59       25        16
- of the narrow ones alone       65       14        21


If we consider these several  cases, we can hardly escape from the 
conclusion that worms show some degree of intelligence in their 
manner of plugging up their burrows.  Each particular object is 
seized in too uniform a manner, and from causes which we can 
generally understand, for the result to be attributed to mere 
chance.  That every object has not been drawn in by its pointed 
end, may be accounted for by labour having been saved through some 
being inserted by their broader or thicker ends.  No doubt worms 
are led by instinct to plug up their burrows; and it might have 
been expected that they would have been led by instinct how best to 
act in each particular case, independently of intelligence.  We see 
how difficult it is to judge whether intelligence comes into play, 
for even plants might sometimes be thought to be thus directed; for 
instance when displaced leaves re-direct their upper surfaces 
towards the light by extremely complicated movements and by the 
shortest course.  With animals, actions appearing due to 
intelligence may be performed through inherited habit without any 
intelligence, although aboriginally thus acquired.  Or the habit 
may have been acquired through the preservation and inheritance of 
beneficial variations of some other habit; and in this case the new 
habit will have been acquired independently of intelligence 
throughout the whole course of its development.  There is no a 
priori improbability in worms having acquired special instincts 
through either of these two latter means.  Nevertheless it is 
incredible that instincts should have been developed in reference 
to objects, such as the leaves of petioles of foreign plants, 
wholly unknown to the progenitors of the worms which act in the 
described manner.  Nor are their actions so unvarying or inevitable 
as are most true instincts.

As worms are not guided by special instincts in each particular 
case, though possessing a general instinct to plug up their 
burrows, and as chance is excluded, the next most probable 
conclusion seems to be that they try in many different ways to draw 
in objects, and at last succeed in some one way.  But it is 
surprising that an animal so low in the scale as a worm should have 
the capacity for acting in this manner, as many higher animals have 
no such capacity.  For instance, ants may be seen vainly trying to 
drag an object transversely to their course, which could be easily 
drawn longitudinally; though after a time they generally act in a 
wiser manner, M. Fabre states {33} that a Sphex--an insect 
belonging to the same highly-endowed order with ants--stocks its 
nest with paralysed grass-hoppers, which are invariably dragged 
into the burrow by their antennae.  When these were cut off close 
to the head, the Sphex seized the palpi; but when these were 
likewise cut off, the attempt to drag its prey into the burrow was 
given up in despair.  The Sphex had not intelligence enough to 
seize one of the six legs or the ovipositor of the grasshopper, 
which, as M. Fabre remarks, would have served equally well.  So 
again, if the paralysed prey with an egg attached to it be taken 
out of the cell, the Sphex after entering and finding the cell 
empty, nevertheless closes it up in the usual elaborate manner.  
Bees will try to escape and go on buzzing for hours on a window, 
one half of which has been left open.  Even a pike continued during 
three months to dash and bruise itself against the glass sides of 
an aquarium, in the vain attempt to seize minnows on the opposite 
side. {34}  A cobra-snake was seen by Mr. Layard {35} to act much 
more wisely than either the pike or the Sphex; it had swallowed a 
toad lying within a hole, and could not withdraw its head; the toad 
was disgorged, and began to crawl away; it was again swallowed and 
again disgorged; and now the snake had learnt by experience, for it 
seized the toad by one of its legs and drew it out of the hole.  
The instincts of even the higher animals are often followed in a 
senseless or purposeless manner:  the weaver-bird will 
perseveringly wind threads through the bars of its cage, as if 
building a nest:  a squirrel will pat nuts on a wooden floor, as if 
he had just buried them in the ground:  a beaver will cut up logs 
of wood and drag them about, though there is no water to dam up; 
and so in many other cases.

Mr. Romanes, who has specially studied the minds of animals, 
believes that we can safely infer intelligence, only when we see an 
individual profiting by its own experience.  By this test the cobra 
showed some intelligence; but this would have been much plainer if 
on a second occasion he had drawn a toad out of a hole by its leg.  
The Sphex failed signally in this respect.  Now if worms try to 
drag objects into their burrows first in one way and then in 
another, until they at last succeed, they profit, at least in each 
particular instance, by experience.

But evidence has been advanced showing that worms do not habitually 
try to draw objects into their burrows in many different ways.  
Thus half-decayed lime-leaves from their flexibility could have 
been drawn in by their middle or basal parts, and were thus drawn 
into the burrows in considerable numbers; yet a large majority were 
drawn in by or near the apex.  The petioles of the Clematis could 
certainly have been drawn in with equal ease by the base and apex; 
yet three times and in certain cases five times as many were drawn 
in by the apex as by the base.  It might have been thought that the 
foot-stalks of leaves would have tempted the worms as a convenient 
handle; yet they are not largely used, except when the base of the 
blade is narrower than the apex.  A large number of the petioles of 
the ash are drawn in by the base; but this part serves the worms as 
food.  In the case of pine-leaves worms plainly show that they at 
least do not seize the leaf by chance; but their choice does not 
appear to be determined by the divergence of the two needles, and 
the consequent advantage or necessity of drawing them into their 
burrows by the base.  With respect to the triangles of paper, those 
which had been drawn in by the apex rarely had their bases creased 
or dirty; and this shows that the worms had not often first tried 
to drag them in by this end.

If worms are able to judge, either before drawing or after having 
drawn an object close to the mouths of their burrows, how best to 
drag it in, they must acquire some notion of its general shape.  
This they probably acquire by touching it in many places with the 
anterior extremity of their bodies, which serves as a tactile 
organ.  It may be well to remember how perfect the sense of touch 
becomes in a man when born blind and deaf, as are worms.  If worms 
have the power of acquiring some notion, however rude, of the shape 
of an object and of their burrows, as seems to be the case, they 
deserve to be called intelligent; for they then act in nearly the 
same manner as would a man under similar circumstances.

To sum up, as chance does not determine the manner in which objects 
are drawn into the burrows, and as the existence of specialized 
instincts for each particular case cannot be admitted, the first 
and most natural supposition is that worms try all methods until 
they at last succeed; but many appearances are opposed to such a 
supposition.  One alternative alone is left, namely, that worms, 
although standing low in the scale of organization, possess some 
degree of intelligence.  This will strike every one as very 
improbable; but it may be doubted whether we know enough about the 
nervous system of the lower animals to justify our natural distrust 
of such a conclusion.  With respect to the small size of the 
cerebral ganglia, we should remember what a mass of inherited 
knowledge, with some power of adapting means to an end, is crowded 
into the minute brain of a worker-ant.

Means by which worms excavate their burrows.--This is effected in 
two ways; by pushing away the earth on all sides, and by swallowing 
it.  In the former case, the worm inserts the stretched out and 
attenuated anterior extremity of its body into any little crevice, 
or hole; and then, as Perrier remarks, {36} the pharynx is pushed 
forwards into this part, which consequently swells and pushes away 
the earth on all sides.  The anterior extremity thus serves as a 
wedge.  It also serves, as we have before seen, for prehension and 
suction, and as a tactile organ.  A worm was placed on loose mould, 
and it buried itself in between two and three minutes.  On another 
occasion four worms disappeared in 15 minutes between the sides of 
the pot and the earth, which had been moderately pressed down.  On 
a third occasion three large worms and a small one were placed on 
loose mould well mixed with fine sand and firmly pressed down, and 
they all disappeared, except the tail of one, in 35 minutes.  On a 
fourth occasion six large worms were placed on argillaceous mud 
mixed with sand firmly pressed down, and they disappeared, except 
the extreme tips of the tails of two of them, in 40 minutes.  In 
none of these cases, did the worms swallow, as far as could be 
seen, any earth.  They generally entered the ground close to the 
sides of the pot.

A pot was next filled with very fine ferruginous sand, which was 
pressed down, well watered, and thus rendered extremely compact.  A 
large worm left on the surface did not succeed in penetrating it 
for some hours, and did not bury itself completely until 25 hrs. 40 
min. had elapsed.  This was effected by the sand being swallowed, 
as was evident by the large quantity ejected from the vent, long 
before the whole body had disappeared.  Castings of a similar 
nature continued to be ejected from the burrow during the whole of 
the following day.

As doubts have been expressed by some writers whether worms ever 
swallow earth solely for the sake of making their burrows, some 
additional cases may be given.  A mass of fine reddish sand, 23 
inches in thickness, left on the ground for nearly two years, had 
been penetrated in many places by worms; and their castings 
consisted partly of the reddish sand and partly of black earth 
brought up from beneath the mass.  This sand had been dug up from a 
considerable depth, and was of so poor a nature that weeds could 
not grow on it.  It is therefore highly improbable that it should 
have been swallowed by the worms as food.  Again in a field near my 
house the castings frequently consist of almost pure chalk, which 
lies at only a little depth beneath the surface; and here again it 
is very improbable that the chalk should have been swallowed for 
the sake of the very little organic matter which could have 
percolated into it from the poor overlying pasture.  Lastly, a 
casting thrown up through the concrete and decayed mortar between 
the tiles, with which the now ruined aisle of Beaulieu Abbey had 
formerly been paved, was washed, so that the coarser matter alone 
was left.  This consisted of grains of quartz, micaceous slate, 
other rocks, and bricks or tiles, many of them from 1/20 to 1/10 
inch in diameter.  No one will suppose that these grains were 
swallowed as food, yet they formed more than half of the casting, 
for they weighed 19 grains, the whole casting having weighed 33 
grains.  Whenever a worm burrows to a depth of some feet in 
undisturbed compact ground, it must form its passage by swallowing 
the earth; for it is incredible that the ground could yield on all 
sides to the pressure of the pharynx when pushed forwards within 
the worm's body.

That worms swallow a larger quantity of earth for the sake of 
extracting any nutritious matter which it may contain than for 
making their burrows, appears to me certain.  But as this old 
belief has been doubted by so high an authority as Claparede, 
evidence in its favour must be given in some detail.  There is no a 
priori improbability in such a belief, for besides other annelids, 
especially the Arenicola marina, which throws up such a profusion 
of castings on our tidal sands, and which it is believed thus 
subsists, there are animals belonging to the most distinct classes, 
which do not burrow, but habitually swallow large quantities of 
sand; namely, the molluscan Onchidium and many Echinoderms. {37}

If earth were swallowed only when worms deepened their burrows or 
made new ones, castings would be thrown up only occasionally; but 
in many places fresh castings may be seen every morning, and the 
amount of earth ejected from the same burrow on successive days is 
large.  Yet worms do not burrow to a great depth, except when the 
weather is very dry or intensely cold.  On my lawn the black 
vegetable mould or humus is only about 5 inches in thickness, and 
overlies light-coloured or reddish clayey soil:  now when castings 
are thrown up in the greatest profusion, only a small proportion 
are light coloured, and it is incredible that the worms should 
daily make fresh burrows in every direction in the thin superficial 
layer of dark-coloured mould, unless they obtained nutriment of 
some kind from it.  I have observed a strictly analogous case in a 
field near my house where bright red clay lay close beneath the 
surface.  Again on one part of the Downs near Winchester the 
vegetable mould overlying the chalk was found to be only from 3 to 
4 inches in thickness; and the many castings here ejected were as 
black as ink and did not effervesce with acids; so that the worms 
must have confined themselves to this thin superficial layer of 
mould, of which large quantities were daily swallowed.  In another 
place at no great distance the castings were white; and why the 
worms should have burrowed into the chalk in some places and not in 
others, I am unable to conjecture.

Two great piles of leaves had been left to decay in my grounds, and 
months after their removal, the bare surface, several yards in 
diameter, was so thickly covered during several months with 
castings that they formed an almost continuous layer; and the large 
number of worms which lived here must have subsisted during these 
months on nutritious matter contained in the black earth.

The lowest layer from another pile of decayed leaves mixed with 
some earth was examined under a high power, and the number of 
spores of various shapes and sizes which it contained was 
astonishingly great; and these crushed in the gizzards of worms may 
largely aid in supporting them.  Whenever castings are thrown up in 
the greatest number, few or no leaves are drawn into the burrows; 
for instance the turf along a hedgerow, about 200 yards in length, 
was daily observed in the autumn during several weeks, and every 
morning many fresh castings were seen; but not a single leaf was 
drawn into these burrows.  These castings from their blackness and 
from the nature of the subsoil could not have been brought up from 
a greater depth than 6 or 8 inches.  On what could these worms have 
subsisted during this whole time, if not on matter contained in the 
black earth?  On the other hand, whenever a large number of leaves 
are drawn into the burrows, the worms seem to subsist chiefly on 
them, for few earth-castings are then ejected on the surface.  This 
difference in the behaviour of worms at different times, perhaps 
explains a statement by Claparede, namely, that triturated leaves 
and earth are always found in distinct parts of their intestines.

Worms sometimes abound in places where they can rarely or never 
obtain dead or living leaves; for instance, beneath the pavement in 
well-swept courtyards, into which leaves are only occasionally 
blown.  My son Horace examined a house, one corner of which had 
subsided; and he found here in the cellar, which was extremely 
damp, many small worm-castings thrown up between the stones with 
which the cellar was paved; and in this case it is improbable that 
the worms could ever have obtained leaves.  Mr. A. C. Horner 
confirms this account, as he has seen castings in the cellars of 
his house, which is an old one at Tonbridge.

But the best evidence, known to me, of worms subsisting for at 
least considerable periods of time solely on the organic matter 
contained in earth, is afforded by some facts communicated to me by 
Dr. King.  Near Nice large castings abound in extraordinary 
numbers, so that 5 or 6 were often found within the space of a 
square foot.  They consist of fine, pale-coloured earth, containing 
calcareous matter, which after having passed through the bodies of 
worms and being dried, coheres with considerable force.  I have 
reason to believe that these castings had been formed by species of 
Perichaeta, which have been naturalized here from the East. {38}  
They rise like towers, with their summits often a little broader 
than their bases, sometimes to a height of above 3 and often to a 
height of 2.5 inches.  The tallest of those which were measured was 
3.3 inches in height and 1 inch in diameter.  A small cylindrical 
passage runs up the centre of each tower, through which the worm 
ascends to eject the earth which it has swallowed, and thus to add 
to its height.  A structure of this kind would not allow leaves 
being easily dragged from the surrounding ground into the burrows; 
and Dr. King, who looked carefully, never saw even a fragment of a 
leaf thus drawn in.  Nor could any trace be discovered of the worms 
having crawled down the exterior surfaces of the towers in search 
of leaves; and had they done so, tracks would almost certainly have 
been left on the upper part whilst it remained soft.  It does not, 
however, follow that these worms do not draw leaves into their 
burrows during some other season of the year, at which time they 
would not build up their towers.

From the several foregoing cases, it can hardly be doubted that 
worms swallow earth, not only for the sake of making their burrows, 
but for obtaining food.  Hensen, however, concludes from his 
analyses of mould that worms probably could not live on ordinary 
vegetable mould, though he admits that they might be nourished to 
some extent by leaf-mould. {39}  But we have seen that worms 
eagerly devour raw meat, fat, and dead worms; and ordinary mould 
can hardly fail to contain many ova, larvae, and small living or 
dead creatures, spores of cryptogamic plants, and micrococci, such 
as those which give rise to saltpetre.  These various organisms, 
together with some cellulose from any leaves and roots not utterly 
decayed, might well account for such large quantities of mould 
being swallowed by worms.  It may be worth while here to recall the 
fact that certain species of Utricularia, which grow in damp places 
in the tropics, possess bladders beautifully constructed for 
catching minute subterranean animals; and these traps would not 
have been developed unless many small animals inhabited such soil.

The depth to which worms penetrate, and the construction of their 
burrows.--Although worms usually live near the surface, yet they 
burrow to a considerable depth during long-continued dry weather 
and severe cold.  In Scandinavia, according to Eisen, and in 
Scotland, according to Mr. Lindsay Carnagie, the burrows run down 
to a depth of from 7 to 8 feet; in North Germany, according to 
Hoffmeister, from 6 to 8 feet, but Hensen says, from 3 to 6 feet.  
This latter observer has seen worms frozen at a depth of 1.5 feet 
beneath the surface.  I have not myself had many opportunities for 
observation, but I have often met with worms at depths of 3 to 4 
feet.  In a bed of fine sand overlying the chalk, which had never 
been disturbed, a worm was cut into two at 55 inches, and another 
was found here at Down in December at the bottom of its burrow, at 
61 inches beneath the surface.  Lastly, in earth near an old Roman 
Villa, which had not been disturbed for many centuries, a worm was 
met with at a depth of 66 inches; and this was in the middle of 
August.

The burrows run down perpendicularly, or more commonly a little 
obliquely.  They are said sometimes to branch, but as far as I have 
seen this does not occur, except in recently dug ground and near 
the surface.  They are generally, or as I believe invariably, lined 
with a thin layer of fine, dark-coloured earth voided by the worms; 
so that they must at first be made a little wider than their 
ultimate diameter.  I have seen several burrows in undisturbed sand 
thus lined at a depth of 4 ft. 6 in.; and others close to the 
surface thus lined in recently dug ground.  The walls of fresh 
burrows are often dotted with little globular pellets of voided 
earth, still soft and viscid; and these, as it appears, are spread 
out on all sides by the worm as it travels up or down its burrow.  
The lining thus formed becomes very compact and smooth when nearly 
dry, and closely fits the worm's body.  The minute reflexed 
bristles which project in rows on all sides from the body, thus 
have excellent points of support; and the burrow is rendered well 
adapted for the rapid movement of the animal.  The lining appears 
also to strengthen the walls, and perhaps saves the worm's body 
from being scratched.  I think so because several burrows which 
passed through a layer of sifted coal-cinders, spread over turf to 
a thickness of 1.5 inch, had been thus lined to an unusual 
thickness.  In this case the worms, judging from the castings, had 
pushed the cinders away on all sides and had not swallowed any of 
them.  In another place, burrows similarly lined, passed through a 
layer of coarse coal-cinders, 3.5 inches in thickness.  We thus see 
that the burrows are not mere excavations, but may rather be 
compared with tunnels lined with cement.

The mouths of the burrow are in addition often lined with leaves; 
and this is an instinct distinct from that of plugging them up, and 
does not appear to have been hitherto noticed.  Many leaves of the 
Scotch-fir or pine (Pinus sylvestris) were given to worms kept in 
confinement in two pots; and when after several weeks the earth was 
carefully broken up, the upper parts of three oblique burrows were 
found surrounded for lengths of 7, 4, and 3.5 inches with pine-
leaves, together with fragments of other leaves which had been 
given the worms as food.  Glass beads and bits of tile, which had 
been strewed on the surface of the soil, were stuck into the 
interstices between the pine-leaves; and these interstices were 
likewise plastered with the viscid castings voided by the worms.  
The structures thus formed cohered so well, that I succeeded in 
removing one with only a little earth adhering to it.  It consisted 
of a slightly curved cylindrical case, the interior of which could 
be seen through holes in the sides and at either end.  The pine-
leaves had all been drawn in by their bases; and the sharp points 
of the needles had been pressed into the lining of voided earth.  
Had this not been effectually done, the sharp points would have 
prevented the retreat of the worms into their burrows; and these 
structures would have resembled traps armed with converging points 
of wire, rendering the ingress of an animal easy and its egress 
difficult or impossible.  The skill shown by these worms is 
noteworthy and is the more remarkable, as the Scotch pine is not a 
native of this district.

After having examined these burrows made by worms in confinement, I 
looked at those in a flower-bed near some Scotch pines.  These had 
all been plugged up in the ordinary manner with the leaves of this 
tree, drawn in for a length of from 1 to 1.5 inch; but the mouths 
of many of them were likewise lined with them, mingled with 
fragments of other kinds of leaves, drawn in to a depth of 4 or 5 
inches.  Worms often remain, as formerly stated, for a long time 
close to the mouths of their burrows, apparently for warmth; and 
the basket-like structures formed of leaves would keep their bodies 
from coming into close contact with the cold damp earth.  That they 
habitually rested on the pine-leaves, was rendered probable by 
their clean and almost polished surfaces.

The burrows which run far down into the ground, generally, or at 
least often, terminate in a little enlargement or chamber.  Here, 
according to Hoffmeister, one or several worms pass the winter 
rolled up into a ball.  Mr. Lindsay Carnagie informed me (1838) 
that he had examined many burrows over a stone-quarry in Scotland, 
where the overlying boulder-clay and mould had recently been 
cleared away, and a little vertical cliff thus left.  In several 
cases the same burrow was a little enlarged at two or three points 
one beneath the other; and all the burrows terminated in a rather 
large chamber, at a depth of 7 or 8 feet from the surface.  These 
chambers contained many small sharp bits of stone and husks of 
flax-seeds.  They must also have contained living seeds, for on the 
following spring Mr. Carnagie saw grass-plants sprouting out of 
some of the intersected chambers.  I found at Abinger in Surrey two 
burrows terminating in similar chambers at a depth of 36 and 41 
inches, and these were lined or paved with little pebbles, about as 
large as mustard seeds; and in one of the chambers there was a 
decayed oat-grain, with its husk.  Hensen likewise states that the 
bottoms of the burrows are lined with little stones; and where 
these could not be procured, seeds, apparently of the pear, had 
been used, as many as fifteen having been carried down into a 
single burrow, one of which had germinated. {40}  We thus see how 
easily a botanist might be deceived who wished to learn how long 
deeply buried seeds remained alive, if he were to collect earth 
from a considerable depth, on the supposition that it could contain 
only seeds which had long lain buried.  It is probable that the 
little stones, as well as the seeds, are carried down from the 
surface by being swallowed; for a surprising number of glass beads, 
bits of tile and of glass were certainly thus carried down by worms 
kept in pots; but some may have been carried down within their 
mouths.  The sole conjecture which I can form why worms line their 
winter-quarters with little stones and seeds, is to prevent their 
closely coiled-up bodies from coming into close contact with the 
surrounding cold soil; and such contact would perhaps interfere 
with their respiration which is effected by the skin alone.

A worm after swallowing earth, whether for making its burrow or for 
food, soon comes to the surface to empty its body.  The ejected 
earth is thoroughly mingled with the intestinal secretions, and is 
thus rendered viscid.  After being dried it sets hard.  I have 
watched worms during the act of ejection, and when the earth was in 
a very liquid state it was ejected in little spurts, and by a slow 
peristaltic movement when not so liquid.  It is not cast 
indifferently on any side, but with some care, first on one and 
then on another side; the tail being used almost like a trowel.  
When a worm comes to the surface to eject earth, the tail 
protrudes, but when it collects leaves its head must protrude.  
Worms therefore must have the power of turning round in their 
closely-fitting burrows; and this, as it appears to us, would be a 
difficult feat.  As soon as a little heap has been formed, the worm 
apparently avoids, for the sake of safety, protruding its tail; and 
the earthy matter is forced up through the previously deposited 
soft mass.  The mouth of the same burrow is used for this purpose 
for a considerable time.  In the case of the tower-like castings 
(see Fig. 2) near Nice, and of the similar but still taller towers 
from Bengal (hereafter to be described and figured), a considerable 
degree of skill is exhibited in their construction.  Dr. King also 
observed that the passage up these towers hardly ever ran in the 
same exact line with the underlying burrow, so that a thin 
cylindrical object such as a haulm of grass, could not be passed 
down the tower into the burrow; and this change of direction 
probably serves in some manner as a protection.

Worms do not always eject their castings on the surface of the 
ground.  When they can find any cavity, as when burrowing in newly 
turned-up earth, or between the stems of banked-up plants, they 
deposit their castings in such places.  So again any hollow beneath 
a large stone lying on the surface of the ground, is soon filled up 
with their castings.  According to Hensen, old burrows are 
habitually used for this purpose; but as far as my experience 
serves, this is not the case, excepting with those near the surface 
in recently dug ground.  I think that Hensen may have been deceived 
by the walls of old burrows, lined with black earth, having sunk in 
or collapsed; for black streaks are thus left, and these are 
conspicuous when passing through light-coloured soil, and might be 
mistaken for completely filled-up burrows.

It is certain that old burrows collapse in the course of time; for 
as we shall see in the next chapter, the fine earth voided by 
worms, if spread out uniformly, would form in many places in the 
course of a year a layer 0.2 of an inch in thickness; so that at 
any rate this large amount is not deposited within the old unused 
burrows.  If the burrows did not collapse, the whole ground would 
be first thickly riddled with holes to a depth of about ten inches, 
and in fifty years a hollow unsupported space, ten inches in depth, 
would be left.  The holes left by the decay of successively formed 
roots of trees and plants must likewise collapse in the course of 
time.

The burrows of worms run down perpendicularly or a little 
obliquely, and where the soil is at all argillaceous, there is no 
difficulty in believing that the walls would slowly flow or slide 
inwards during very wet weather.  When, however, the soil is sandy 
or mingled with many small stones, it can hardly be viscous enough 
to flow inwards during even the wettest weather; but another agency 
may here come into play.  After much rain the ground swells, and as 
it cannot expand laterally, the surface rises; during dry weather 
it sinks again.  For instance, a large flat stone laid on the 
surface of a field sank 3.33 mm. whilst the weather was dry between 
May 9th and June 13th, and rose 1.91 mm, between September 7th and 
19th of the same year, much rain having fallen during the latter 
part of this time.  During frosts and thaws the movements were 
twice as great.  These observations were made by my son Horace, who 
will hereafter publish an account of the movements of this stone 
during successive wet and dry seasons, and of the effects of its 
being undermined by worms.  Now when the ground swells, if it be 
penetrated by cylindrical holes, such as worm-burrows, their walls 
will tend to yield and be pressed inwards; and the yielding will be 
greater in the deeper parts (supposing the whole to be equally 
moistened) from the greater weight of the superincumbent soil which 
has to be raised, than in the parts near the surface.  When the 
ground dries, the walls will shrink a little and the burrows will 
be a little enlarged.  Their enlargement, however, through the 
lateral contraction of the ground, will not be favoured, but rather 
opposed, by the weight of the superincumbent soil.

Distribution of Worms.--Earth-worms are found in all parts of the 
world, and some of the genera have an enormous range. {41}  They 
inhabit the most isolated islands; they abound in Iceland, and are 
known to exist in the West Indies, St. Helena, Madagascar, New 
Caledonia and Tahiti.  In the Antarctic regions, worms from 
Kerguelen Land have been described by Ray Lankester; and I found 
them in the Falkland Islands.  How they reach such isolated islands 
is at present quite unknown.  They are easily killed by salt-water, 
and it does not appear probable that young worms or their egg-
capsules could be carried in earth adhering to the feet or beaks of 
land-birds.  Moreover Kerguelen Land is not now inhabited by any 
land-bird.

In this volume we are chiefly concerned with the earth cast up by 
worms, and I have gleaned a few facts on this subject with respect 
to distant lands.  Worms throw up plenty of castings in the United 
States.  In Venezuela, castings, probably ejected by species of 
Urochaeta, are common in the gardens and fields, but not in the 
forests, as I hear from Dr. Ernst of Caracas.  He collected 156 
castings from the court-yard of his house, having an area of 200 
square yards.  They varied in bulk from half a cubic centimeter to 
five cubic centimeters, and were on an average three cubic 
centimeters.  They were, therefore, of small size in comparison 
with those often found in England; for six large castings from a 
field near my house averaged 16 cubic centimeters.  Several species 
of earth-worms are common in St. Catharina in South Brazil, and 
Fritz Muller informs me "that in most parts of the forests and 
pasture-lands, the whole soil, to a depth of a quarter of a metre, 
looks as if it had passed repeatedly through the intestines of 
earth-worms, even where hardly any castings are to be seen on the 
surface."  A gigantic but very rare species is found there, the 
burrows of which are sometimes even two centimeters or nearly 0.8 
of an inch in diameter, and which apparently penetrate the ground 
to a great depth.

In the dry climate of New South Wales, I hardly expected that worms 
would be common; but Dr. G. Krefft of Sydney, to whom I applied, 
after making inquiries from gardeners and others, and from his own 
observations, informs me that their castings abound.  He sent me 
some collected after heavy rain, and they consisted of little 
pellets, about 0.15 inch in diameter; and the blackened sandy earth 
of which they were formed still cohered with considerable tenacity.

The late Mr. John Scott of the Botanic Gardens near Calcutta made 
many observations for me on worms living under the hot and humid 
climate of Bengal.  The castings abound almost everywhere, in 
jungles and in the open ground, to a greater degree, as he thinks, 
than in England.  After the water has subsided from the flooded 
rice-fields, the whole surface very soon becomes studded with 
castings--a fact which much surprised Mr. Scott, as he did not know 
how long worms could survive beneath water.  They cause much 
trouble in the Botanic garden, "for some of the finest of our lawns 
can be kept in anything like order only by being almost daily 
rolled; if left undisturbed for a few days they become studded with 
large castings."  These closely resemble those described as 
abounding near Nice; and they are probably the work of a species of 
Perichaeta.  They stand up like towers, with an open passage in the 
centre.

A figure of one of these castings from a photograph is here given 
(Fig. 3).  The largest received by me was 3.5 inches in height and 
1.35 inch in diameter; another was only 0.75 inch in diameter and 
2.75 in height.  In the following year, Mr. Scott measured several 
of the largest; one was 6 inches in height and nearly 1.5 in 
diameter:  two others were 5 inches in height and respectively 2 
and rather more than 2.5 inches in diameter.  The average weight of 
the 22 castings sent to me was 35 grammes (1.25 oz.); and one of 
them weighed 44.8 grammes (or 2 oz.). All these castings were 
thrown up either in one night or in two.  Where the ground in 
Bengal is dry, as under large trees, castings of a different kind 
are found in vast numbers:  these consist of little oval or conical 
bodies, from about the 1/20 to rather above 1/10 of an inch in 
length.  They are obviously voided by a distinct species of worms.

The period during which worms near Calcutta display such 
extraordinary activity lasts for only a little over two months, 
namely, during the cool season after the rains.  At this time they 
are generally found within about 10 inches beneath the surface.  
During the hot season they burrow to a greater depth, and are then 
found coiled up and apparently hybernating.  Mr. Scott has never 
seen them at a greater depth than 2.5 feet, but has heard of their 
having been found at 4 feet.  Within the forests, fresh castings 
may be found even during the hot season.  The worms in the Botanic 
garden, during the cool and dry season, draw many leaves and little 
sticks into the mouths of their burrows, like our English worms; 
but they rarely act in this manner during the rainy season.

Mr. Scott saw worm-castings on the lofty mountains of Sikkim in 
North India.  In South India Dr. King found in one place, on the 
plateau of the Nilgiris, at an elevation of 7000 feet, "a good many 
castings," which are interesting for their great size.  The worms 
which eject them are seen only during the wet season, and are 
reported to be from 12 to 15 inches in length, and as thick as a 
man's little finger.  These castings were collected by Dr. King 
after a period of 110 days without any rain; and they must have 
been ejected either during the north-east or more probably during 
the previous south-west monsoon; for their surfaces had suffered 
some disintegration and they were penetrated by many fine roots.  A 
drawing is here given (Fig. 4) of one which seems to have best 
retained its original size and appearance.  Notwithstanding some 
loss from disintegration, five of the largest of these castings 
(after having been well sun-dried) weighed each on an average 89.5 
grammes, or above 3 oz.; and the largest weighed 123.14 grammes, or 
4.33 oz.,--that is, above a quarter of a pound!  The largest 
convolutions were rather more than one inch in diameter; but it is 
probable that they had subsided a little whilst soft, and that 
their diameters had thus been increased.  Some had flowed so much 
that they now consisted of a pile of almost flat confluent cakes.  
All were formed of fine, rather light-coloured earth, and were 
surprisingly hard and compact, owing no doubt to the animal matter 
by which the particles of earth had been cemented together.  They 
did not disintegrate, even when left for some hours in water.  
Although they had been cast up on the surface of gravelly soil, 
they contained extremely few bits of rock, the largest of which was 
only 0.15 inch in diameter.

Dr. King saw in Ceylon a worm about 2 feet in length and 0.5 inch 
in diameter; and he was told that it was a very common species 
during the wet season.  These worms must throw up castings at least 
as large as those on the Nilgiri Mountains; but Dr. King saw none 
during his short visit to Ceylon.

Sufficient facts have now been given, showing that worms do much 
work in bringing up fine earth to the surface in most or all parts 
of the world, and under the most different climates.



CHAPTER III--THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE 
SURFACE.



Rate at which various objects strewed on the surface of grass-
fields are covered up by the castings of worms--The burial of a 
paved path--The slow subsidence of great stones left on the 
surface--The number of worms which live within a given space--The 
weight of earth ejected from a burrow, and from all the burrows 
within a given space--The thickness of the layer of mould which the 
castings on a given space would form within a given time if 
uniformly spread out--The slow rate at which mould can increase to 
a great thickness--Conclusion.


We now come to the more immediate subject of this volume, namely, 
the amount of earth which is brought up by worms from beneath the 
surface, and is afterwards spread out more or less completely by 
the rain and wind.  The amount can be judged of by two methods,--by 
the rate at which objects left on the surface are buried, and more 
accurately by weighing the quantity brought up within a given time.  
We will begin with the first method, as it was first followed.

Near Mael Hall in Staffordshire, quick-lime had been spread about 
the year 1827 thickly over a field of good pasture-land, which had 
not since been ploughed.  Some square holes were dug in this field 
in the beginning of October 1837; and the sections showed a layer 
of turf, formed by the matted roots of the grasses, 0.5 inch in 
thickness, beneath which, at a depth of 2.5 inches (or 3 inches 
from the surface), a layer of the lime in powder or in small lumps 
could be distinctly seen running all round the vertical sides of 
the holes.  The soil beneath the layer of lime was either gravelly 
or of a coarse sandy nature, and differed considerably in 
appearance from the overlying dark-coloured fine mould.  Coal-
cinders had been spread over a part of this same field either in 
the year 1833 or 1834; and when the above holes were dug, that is 
after an interval of 3 or 4 years, the cinders formed a line of 
black spots round the holes, at a depth of 1 inch beneath the 
surface, parallel to and above the white layer of lime.  Over 
another part of this field cinders had been strewed, only about 
half-a-year before, and these either still lay on the surface or 
were entangled among the roots of the grasses; and I here saw the 
commencement of the burying process, for worm-castings had been 
heaped on several of the smaller fragments.  After an interval of 
4.75 years this field was re-examined, and now the two layers of 
lime and cinders were found almost everywhere at a greater depth 
than before by nearly 1 inch, we will say by 0.75 of an inch.  
Therefore mould to an average thickness of 0.22 of an inch had been 
annually brought up by the worms, and had been spread over the 
surface of this field.

Coal-cinders had been strewed over another field, at a date which 
could not be positively ascertained, so thickly that they formed 
(October, 1837) a layer, 1 inch in thickness at a depth of about 3 
inches from the surface.  The layer was so continuous that the 
over-lying dark vegetable mould was connected with the sub-soil of 
red clay only by the roots of the grasses; and when these were 
broken, the mould and the red clay fell apart.  In a third field, 
on which coal-cinders and burnt marl had been strewed several times 
at unknown dates, holes were dug in 1842; and a layer of cinders 
could be traced at a depth of 3.5 inches, beneath which at a depth 
of 9.5 inches from the surface there was a line of cinders together 
with burnt marl.  On the sides of one hole there were two layers of 
cinders, at 2 and 3.5 inches beneath the surface; and below them at 
a depth in parts of 9.5, and in other parts of 10.5 inches there 
were fragments of burnt marl.  In a fourth field two layers of 
lime, one above the other, could be distinctly traced, and beneath 
them a layer of cinders and burnt marl at a depth of from 10 to 12 
inches below the surface.

A piece of waste, swampy land was enclosed, drained, ploughed, 
harrowed and thickly covered in the year 1822 with burnt marl and 
cinders.  It was sowed with grass seeds, and now supports a 
tolerably good but coarse pasture.  Holes were dug in this field in 
1837, or 15 years after its reclamation, and we see in the 
accompanying diagram (Fig. 5), reduced to half of the natural 
scale, that the turf was 1 inch thick, beneath which there was a 
layer of vegetable mould 2.5 inches thick.  This layer did not 
contain fragments of any kind; but beneath it there was a layer of 
mould, 1.5 inch in thickness, full of fragments of burnt marl, 
conspicuous from their red colour, one of which near the bottom was 
an inch in length; and other fragments of coal-cinders together 
with a few white quartz pebbles.  Beneath this layer and at a depth 
of 4.5 inches from the surface, the original black, peaty, sandy 
soil with a few quartz pebbles was encountered.  Here therefore the 
fragments of burnt marl and cinders had been covered in the course 
of 15 years by a layer of fine vegetable mould, only 2.5 inches in 
thickness, excluding the turf.  Six and a half years subsequently 
this field was re-examined, and the fragments were now found at 
from 4 to 5 inches beneath the surface.  So that in this interval 
of 6.5 years, about 1.5 inch of mould had been added to the 
superficial layer.  I am surprised that a greater quantity had not 
been brought up during the whole 21.5 years, for in the closely 
underlying black, peaty soil there were many worms.  It is, 
however, probable that formerly, whilst the land remained poor, 
worms were scanty; and the mould would then have accumulated 
slowly.  The average annual increase of thickness for the whole 
period is 0.19 of an inch.

Two other cases are worth recording.  In the spring of 1835, a 
field, which had long existed as poor pasture and was so swampy 
that it trembled slightly when stamped on, was thickly covered with 
red sand so that the whole surface appeared at first bright red.  
When holes were dug in this field after an interval of about 2.5 
years, the sand formed a layer at a depth of 0.75 in. beneath the 
surface.  In 1842 (i.e., 7 years after the sand had been laid on) 
fresh holes were dug, and now the red sand formed a distinct layer, 
2 inches beneath the surface, or 1.5 inch beneath the turf; so that 
on an average, 0.21 inch of mould had been annually brought to the 
surface.  Immediately beneath the layer of red sand, the original 
substratum of black sandy peat extended.

A grass field, likewise not far from Maer Hall, had formerly been 
thickly covered with marl, and was then left for several years as 
pasture; it was afterwards ploughed.  A friend had three trenches 
dug in this field 28 years after the application of the marl, {42} 
and a layer of the marl fragments could be traced at a depth, 
carefully measured, of 12 inches in some parts, and of 14 inches in 
other parts.  This difference in depth depended on the layer being 
horizontal, whilst the surface consisted of ridges and furrows from 
the field having been ploughed.  The tenant assured me that it had 
never been turned up to a greater depth than from 6 to 8 inches; 
and as the fragments formed an unbroken horizontal layer from 12 to 
14 inches beneath the surface, these must have been buried by the 
worms whilst the land was in pasture before it was ploughed, for 
otherwise they would have been indiscriminately scattered by the 
plough throughout the whole thickness of the soil.  Four-and-a-half 
years afterwards I had three holes dug in this field, in which 
potatoes had been lately planted, and the layer of marl-fragments 
was now found 13 inches beneath the bottoms of the furrows, and 
therefore probably 15 inches beneath the general level of the 
field.  It should, however, be observed that the thickness of the 
blackish sandy soil, which had been thrown up by the worms above 
the marl-fragments in the course of 32.5 years, would have measured 
less than 15 inches, if the field had always remained as pasture, 
for the soil would in this case have been much more compact.  The 
fragments of marl almost rested on an undisturbed substratum of 
white sand with quartz pebbles; and as this would be little 
attractive to worms, the mould would hereafter be very slowly 
increased by their action.

We will now give some cases of the action of worms, on land 
differing widely from the dry sandy or the swampy pastures just 
described.  The chalk formation extends all round my house in Kent; 
and its surface, from having been exposed during an immense period 
to the dissolving action of rain-water, is extremely irregular, 
being abruptly festooned and penetrated by many deep well-like 
cavities. {43}  During the dissolution of the chalk, the insoluble 
matter, including a vast number of unrolled flints of all sizes, 
has been left on the surface and forms a bed of stiff red clay, 
full of flints, and generally from 6 to 14 feet in thickness.  Over 
the red clay, wherever the land has long remained as pasture, there 
is a layer a few inches in thickness, of dark-coloured vegetable 
mould.

A quantity of broken chalk was spread, on December 20, 1842, over a 
part of a field near my house, which had existed as pasture 
certainly for 30, probably for twice or thrice as many years.  The 
chalk was laid on the land for the sake of observing at some future 
period to what depth it would become buried.  At the end of 
November, 1871, that is after an interval of 29 years, a trench was 
dug across this part of the field; and a line of white nodules 
could be traced on both sides of the trench, at a depth of 7 inches 
from the surface.  The mould, therefore, (excluding the turf) had 
here been thrown up at an average rate of 0.22 inch per year.  
Beneath the line of chalk nodules there was in parts hardly any 
fine earth free of flints, while in other parts there was a layer, 
2.25 inches in thickness.  In this latter case the mould was 
altogether 9.25 inches thick; and in one such spot a nodule of 
chalk and a smooth flint pebble, both of which must have been left 
at some former time on the surface, were found at this depth.  At 
from 11 to 12 inches beneath the surface, the undisturbed reddish 
clay, full of flints, extended.  The appearance of the above 
nodules of chalk surprised me, much at first, as they closely 
resembled water-worn pebbles, whereas the freshly-broken fragments 
had been angular.  But on examining the nodules with a lens, they 
no longer appeared water-worn, for their surfaces were pitted 
through unequal corrosion, and minute, sharp points, formed of 
broken fossil shells, projected from them.  It was evident that the 
corners of the original fragments of chalk had been wholly 
dissolved, from presenting a large surface to the carbonic acid 
dissolved in the rain-water and to that generated in soil 
containing vegetable matter, as well as to the humus-acids. {44}  
The projecting corners would also, relatively to the other parts, 
have been embraced by a larger number of living rootlets; and these 
have the power of even attacking marble, as Sachs has shown.  Thus, 
in the course of 29 years, buried angular fragments of chalk had 
been converted into well-rounded nodules.

Another part of this same field was mossy, and as it was thought 
that sifted coal-cinders would improve the pasture, a thick layer 
was spread over this part either in 1842 or 1843, and another layer 
some years afterwards.  In 1871 a trench was here dug, and many 
cinders lay in a line at a depth of 7 inches beneath the surface, 
with another line at a depth of 5.5 inches parallel to the one 
beneath.  In another part of this field, which had formerly existed 
as a separate one, and which it was believed had been pasture-land 
for more than a century, trenches were dug to see how thick the 
vegetable mould was.  By chance the first trench was made at a spot 
where at some former period, certainly more than forty years 
before, a large hole had been filled up with coarse red clay, 
flints, fragments of chalk, and gravel; and here the fine vegetable 
mould was only from 4.125 to 4.375 inches in thickness.  In another 
and undisturbed place, the mould varied much in thickness, namely, 
from 6.5 to 8.5 inches; beneath which a few small fragments of 
brick were found in one place.  From these several cases, it would 
appear that during the last 29 years mould has been heaped on the 
surface at an average annual rate of from 0.2 to 0.22 of an inch.  
But in this district when a ploughed field is first laid down in 
grass, the mould accumulates at a much slower rate.  The rate, 
also, must become very much slower after a bed of mould, several 
inches in thickness, has been formed; for the worms then live 
chiefly near the surface, and burrow down to a greater depth so as 
to bring up fresh earth from below, only during the winter when the 
weather is very cold (at which time worms were found in this field 
at a depth of 26 inches) and during summer, when the weather is 
very dry.

A field, which adjoins the one just described, slopes in one part 
rather steeply (viz., at from 10 degrees to 15 degrees); this part 
was last ploughed in 1841, was then harrowed and left to become 
pasture-land.  For several years it was clothed with an extremely 
scant vegetation, and was so thickly covered with small and large 
flints (some of them half as large as a child's head) that the 
field was always called by my sons "the stony field."  When they 
ran down the slope the stones clattered together, I remember 
doubting whether I should live to see these larger flints covered 
with vegetable mould and turf.  But the smaller stones disappeared 
before many years had elapsed, as did every one of the larger ones 
after a time; so that after thirty years (1871) a horse could 
gallop over the compact turf from one end of the field to the 
other, and not strike a single stone with his shoes.  To anyone who 
remembered the appearance of the field in 1842, the transformation 
was wonderful.  This was certainly the work of the worms, for 
though castings were not frequent for several years, yet some were 
thrown up month after month, and these gradually increased in 
numbers as the pasture improved.  In the year 1871 a trench was dug 
on the above slope, and the blades of grass were cut off close to 
the roots, so that the thickness of the turf and of the vegetable 
mould could be measured accurately.  The turf was rather less than 
half an inch, and the mould, which did not contain any stones, 2.5 
inches in thickness.  Beneath this lay coarse clayey earth full of 
flints, like that in any of the neighbouring ploughed fields.  This 
coarse earth easily fell apart from the overlying mould when a spit 
was lifted up.  The average rate of accumulation of the mould 
during the whole thirty years was only .083 inch per year (i.e., 
nearly one inch in twelve years); but the rate must have been much 
slower at first, and afterwards considerably quicker.

The transformation in the appearance of this field, which had been 
effected beneath my eyes, was afterwards rendered the more 
striking, when I examined in Knole Park a dense forest of lofty 
beech-trees, beneath which nothing grew.  Here the ground was 
thickly strewed with large naked stones, and worm-castings were 
almost wholly absent.  Obscure lines and irregularities on the 
surface indicated that the land had been cultivated some centuries 
ago.  It is probable that a thick wood of young beech-trees sprung 
up so quickly, that time enough was not allowed for worms to cover 
up the stones with their castings, before the site became unfitted 
for their existence.  Anyhow the contrast between the state of the 
now miscalled "stony field," well stocked with worms, and the 
present state of the ground beneath the old beech-trees in Knole 
Park, where worms appeared to be absent, was striking.

A narrow path running across part of my lawn was paved in 1843 with 
small flagstones, set edgeways; but worms threw up many castings 
and weeds grew thickly between them.  During several years the path 
was weeded and swept; but ultimately the weeds and worms prevailed, 
and the gardener ceased to sweep, merely mowing off the weeds, as 
often as the lawn was mowed.  The path soon became almost covered 
up, and after several years no trace of it was left.  On removing, 
in 1877, the thin overlying layer of turf, the small flag-stones, 
all in their proper places, were found covered by an inch of fine 
mould.

Two recently published accounts of substances strewed on the 
surface of pasture-land, having become buried through the action of 
worms, may be here noticed.  The Rev. H. C. Key had a ditch cut in 
a field, over which coal-ashes had been spread, as it was believed, 
eighteen years before; and on the clean-cut perpendicular sides of 
the ditch, at a depth of at least seven inches, there could be 
seen, for a length of 60 yards, "a distinct, very even, narrow line 
of coal-ashes, mixed with small coal, perfectly parallel with the 
top-sward." {45}  This parallelism and the length of the section 
give interest to the case.  Secondly, Mr. Dancer states {46} that 
crushed bones had been thickly strewed over a field; and "some 
years afterwards" these were found "several inches below the 
surface, at a uniform depth."

The Rev. Mr. Zincke informs me that he has lately had an orchard 
dug to the unusual depth of 4 feet.  The upper 18 inches consisted 
of dark-coloured vegetable mould, and the next 18 inches of sandy 
loam, containing in the lower part many rolled pieces of sandstone, 
with some bits of brick and tile, probably of Roman origin, as 
remains of this period have been found close by.  The sandy loam 
rested on an indurated ferruginous pan of yellow clay, on the 
surface of which two perfect celts were found.  If, as seems 
probable, the celts were originally left on the surface of the 
land, they have since been covered up with earth 3 feet in 
thickness, all of which has probably passed through the bodies of 
worms, excepting the stones which may have been scattered on the 
surface at different times, together with manure or by other means.  
It is difficult otherwise to understand the source of the 18 inches 
of sandy loam, which differed from the overlying dark vegetable 
mould, after both had been burnt, only in being of a brighter red 
colour, and in not being quite so fine-grained.  But on this view 
we must suppose that the carbon in vegetable mould, when it lies at 
some little depth beneath the surface and does not continually 
receive decaying vegetable matter from above, loses its dark colour 
in the course of centuries; but whether this is probable I do not 
know.

Worms appear to act in the same manner in New Zealand as in Europe; 
for Professor J. von Haast has described {47} a section near the 
coast, consisting of mica-schist, "covered by 5 or 6 feet of loess, 
above which about 12 inches of vegetable soil had accumulated."  
Between the loess and the mould there was a layer from 3 to 6 
inches in thickness, consisting of "cores, implements, flakes, and 
chips, all manufactured from hard basaltic rock."  It is therefore 
probable that the aborigines, at some former period, had left these 
objects on the surface, and that they had afterwards been slowly 
covered up by the castings of worms.

Farmers in England are well aware that objects of all kinds, left 
on the surface of pasture-land, after a time disappear, or, as they 
say, work themselves downwards.  How powdered lime, cinders, and 
heavy stones, can work down, and at the same rate, through the 
matted roots of a grass-covered surface, is a question which has 
probably never occurred to them. {48}

The Sinking of great Stones through the Action of Worms.--When a 
stone of large size and of irregular shape is left on the surface 
of the ground, it rests, of course, on the more protuberant parts; 
but worms soon fill up with their castings all the hollow spaces on 
the lower side; for, as Hensen remarks, they like the shelter of 
stones.  As soon as the hollows are filled up, the worms eject the 
earth which they have swallowed beyond the circumference of the 
stones; and thus the surface of the ground is raised all round the 
stone.  As the burrows excavated directly beneath the stone after a 
time collapse, the stone sinks a little. {49}  Hence it is, that 
boulders which at some ancient period have rolled down from a rocky 
mountain or cliff on to a meadow at its base, are always somewhat 
imbedded in the soil; and, when removed, leave an exact impression 
of their lower surfaces in the underlying fine mould.  If, however, 
a boulder is of such huge dimensions, that the earth beneath is 
kept dry, such earth will not be inhabited by worms, and the 
boulder will not sink into the ground.

A lime-kiln formerly stood in a grass-field near Leith Hill Place 
in Surrey, and was pulled down 35 years before my visit; all the 
loose rubbish had been carted away, excepting three large stones of 
quartzose sandstone, which it was thought might hereafter be of 
some use.  An old workman remembered that they had been left on a 
bare surface of broken bricks and mortar, close to the foundations 
of the kiln; but the whole surrounding surface is now covered with 
turf and mould.  The two largest of these stones had never since 
been moved; nor could this easily have been done, as, when I had 
them removed, it was the work of two men with levers.  One of these 
stones, and not the largest, was 64 inches long, 17 inches broad, 
and from 9 to 10 inches in thickness.  Its lower surface was 
somewhat protuberant in the middle; and this part still rested on 
broken bricks and mortar, showing the truth of the old workman's 
account.  Beneath the brick rubbish the natural sandy soil, full of 
fragments of sandstone was found; and this could have yielded very 
little, if at all, to the weight of the stone, as might have been 
expected if the sub-soil had been clay.  The surface of the field, 
for a distance of about 9 inches round the stone, gradually sloped 
up to it, and close to the stone stood in most places about 4 
inches above the surrounding ground.  The base of the stone was 
buried from 1 to 2 inches beneath the general level, and the upper 
surface projected about 8 inches above this level, or about 4 
inches above the sloping border of turf.  After the removal of the 
stone it became evident that one of its pointed ends must at first 
have stood clear above the ground by some inches, but its upper 
surface was now on a level with the surrounding turf.  When the 
stone was removed, an exact cast of its lower side, forming a 
shallow crateriform hollow, was left, the inner surface of which 
consisted of fine black mould, excepting where the more protuberant 
parts rested on the brick-rubbish.  A transverse section of this 
stone, together with its bed, drawn from measurements made after it 
had been displaced, is here given on a scale of 0.5 inch to a foot 
(Fig. 6).  The turf-covered border which sloped up to the stone, 
consisted of fine vegetable mould, in one part 7 inches in 
thickness.  This evidently consisted of worm-castings, several of 
which had been recently ejected.  The whole stone had sunk in the 
thirty-five years, as far as I could judge, about 1.5 inch; and 
this must have been due to the brick-rubbish beneath the more 
protuberant parts having been undermined by worms.  At this rate 
the upper surface of the stone, if it had been left undisturbed, 
would have sunk to the general level of the field in 247 years; but 
before this could have occurred, some earth would have been washed 
down by heavy rain from the castings on the raised border of turf 
over the upper surface of the stone.

The second stone was larger that the one just described, viz., 67 
inches in length, 39 in breadth, and 15 in thickness.  The lower 
surface was nearly flat, so that the worms must soon have been 
compelled to eject their castings beyond its circumference.  The 
stone as a whole had sunk about 2 inches into the ground.  At this 
rate it would have required 262 years for its upper surface to have 
sunk to the general level of the field.  The upwardly sloping, 
turf-covered border round the stone was broader than in the last 
case, viz., from 14 to 16 inches; and why this should be so, I 
could see no reason.  In most parts this border was not so high as 
in the last case, viz., from 2 to 2.5 inches, but in one place it 
was as much as 5.5.  Its average height close to the stone was 
probably about 3 inches, and it thinned out to nothing.  If so, a 
layer of fine earth, 15 inches in breadth and 1.5 inch in average 
thickness, of sufficient length to surround the whole of the much 
elongated slab, must have been brought up by the worms in chief 
part from beneath the stone in the course of 35 years.  This amount 
would be amply sufficient to account for its having sunk about 2 
inches into the ground; more especially if we bear in mind that a 
good deal of the finest earth would have been washed by heavy rain 
from the castings ejected on the sloping border down to the level 
of the field.  Some fresh castings were seen close to the stone.  
Nevertheless, on digging a large hole to a depth of 18 inches where 
the stone had lain, only two worms and a few burrows were seen, 
although the soil was damp and seemed favourable for worms.  There 
were some large colonies of ants beneath the stone, and possibly 
since their establishment the worms had decreased in number.

The third stone was only about half as large as the others; and two 
strong boys could together have rolled it over.  I have no doubt 
that it had been rolled over at a moderately recent time, for it 
now lay at some distance from the two other stones at the bottom of 
a little adjoining slope.  It rested also on fine earth, instead of 
partly on brick-rubbish.  In agreement with this conclusion, the 
raised surrounding border of turf was only 1 inch high in some 
parts, and 2 inches in other parts.  There were no colonies of ants 
beneath this stone, and on digging a hole where it had lain, 
several burrows and worms were found.

At Stonehenge, some of the outer Druidical stones are now 
prostrate, having fallen at a remote but unknown period; and these 
have become buried to a moderate depth in the ground.  They are 
surrounded by sloping borders of turf, on which recent castings 
were seen.  Close to one of these fallen stones, which was 17 ft 
long, 6 ft. broad, and 28.5 inches thick, a hole was dug; and here 
the vegetable mould was at least 9.5 inches in thickness.  At this 
depth a flint was found, and a little higher up on one side of the 
hole a fragment of glass.  The base of the stone lay about 9.5 
inches beneath the level of the surrounding ground, and its upper 
surface 19 inches above the ground.

A hole was also dug close to a second huge stone, which in falling 
had broken into two pieces; and this must have happened long ago, 
judging from the weathered aspect of the fractured ends.  The base 
was buried to a depth of 10 inches, as was ascertained by driving 
an iron skewer horizontally into the ground beneath it.  The 
vegetable mould forming the turf-covered sloping border round the 
stone, on which many castings had recently been ejected, was 10 
inches in thickness; and most of this mould must have been brought 
up by worms from beneath its base.  At a distance of 8 yards from 
the stone, the mould was only 5.5 inches in thickness (with a piece 
of tobacco pipe at a depth of 4 inches), and this rested on broken 
flint and chalk which could not have easily yielded to the pressure 
or weight of the stone.

A straight rod was fixed horizontally (by the aid of a spirit-
level) across a third fallen stone, which was 7 feet 9 inches long; 
and the contour of the projecting parts and of the adjoining 
ground, which was not quite level, was thus ascertained, as shown 
in the accompanying diagram (Fig. 7) on a scale of 0.5 inch to a 
foot.  The turf-covered border sloped up to the stone on one side 
to a height of 4 inches, and on the opposite side to only 2.5 
inches above the general level.  A hole was dug on the eastern 
side, and the base of the stone was here found to lie at a depth of 
4 inches beneath the general level of the ground, and of 8 inches 
beneath the top of the sloping turf-covered border.


Sufficient evidence has now been given showing that small objects 
left on the surface of the land where worms abound soon get buried, 
and that large stones sink slowly downwards through the same means.  
Every step of the process could be followed, from the accidental 
deposition of a single casting on a small object lying loose on the 
surface, to its being entangled amidst the matted roots of the 
turf, and lastly to its being embedded in the mould at various 
depths beneath the surface.  When the same field was re-examined 
after the interval of a few years, such objects were found at a 
greater depth than before.  The straightness and regularity of the 
lines formed by the imbedded objects, and their parallelism with 
the surface of the land, are the most striking features of the 
case; for this parallelism shows how equably the worms must have 
worked; the result being, however, partly the effect of the washing 
down of the fresh castings by rain.  The specific gravity of the 
objects does not affect their rate of sinking, as could be seen by 
porous cinders, burnt marl, chalk and quartz pebbles, having all 
sunk to the same depth within the same time.  Considering the 
nature of the substratum, which at Leith Hill Place was sandy soil 
including many bits of rock, and at Stonehenge, chalk-rubble with 
broken flints; considering, also, the presence of the turf-covered 
sloping border of mould round the great fragments of stone at both 
these places, their sinking does not appear to have been sensibly 
aided by their weight, though this was considerable. {50}

On the number of worms which live within a given space.--We will 
now show, firstly, what a vast number of worms live unseen by us 
beneath our feet, and, secondly, the actual weight of the earth 
which they bring up to the surface within a given space and within 
a given time.  Hensen, who has published so full and interesting an 
account of the habits of worms, {51} calculates, from the number 
which he found in a measured space, that there must exist 133,000 
living worms in a hectare of land, or 53,767 in an acre.  This 
latter number of worms would weigh 356 pounds, taking Hensen's 
standard of the weight of a single worm, namely, three grams.  It 
should, however, be noted that this calculation is founded on the 
numbers found in a garden, and Hensen believes that worms are here 
twice as numerous as in corn-fields.  The above result, astonishing 
though it be, seems to me credible, judging from the number of 
worms which I have sometimes seen, and from the number daily 
destroyed by birds without the species being exterminated.  Some 
barrels of bad ale were left on Mr. Miller's land, {52} in the hope 
of making vinegar, but the vinegar proved bad, and the barrels were 
upset.  It should be premised that acetic acid is so deadly a 
poison to worms that Perrier found that a glass rod dipped into 
this acid and then into a considerable body of water in which worms 
were immersed, invariably killed them quickly.  On the morning 
after the barrels had been upset, "the heaps of worms which lay 
dead on the ground were so amazing, that if Mr. Miller had not seen 
them, he could not have thought it possible for such numbers to 
have existed in the space."  As further evidence of the large 
number of worms which live in the ground, Hensen states that he 
found in a garden sixty-four open burrows in a space of 14.5 square 
feet, that is, nine in 2 square feet.  But the burrows are 
sometimes much more numerous, for when digging in a grass-field 
near Maer Hall, I found a cake of dry earth, as large as my two 
open hands, which was penetrated by seven burrows, as large as 
goose-quills.

Weight of the earth ejected from a single burrow, and from all the 
burrows within a given space.--With respect to the weight of the 
earth daily ejected by worms, Hensen found that it amounted, in the 
case of some worms which he kept in confinement, and which he 
appears to have fed with leaves, to only 0.5 gram, or less than 8 
grains per diem.  But a very much larger amount must be ejected by 
worms in their natural state, at the periods when they consume 
earth as food instead of leaves, and when they are making deep 
burrows.  This is rendered almost certain by the following weights 
of the castings thrown up at the mouths of single burrows; the 
whole of which appeared to have been ejected within no long time, 
as was certainly the case in several instances.  The castings were 
dried (excepting in one specified instance) by exposure during many 
days to the sun or before a hot fire.


WEIGHT OF THE CASTINGS ACCUMULATED AT THE MOUTH OF A SINGLE BURROW.


(Weight in ounces given in parenthesis--DP.)

(1.)  Down, Kent (sub-soil red clay, full of flints, over-lying the 
chalk).  The largest casting which I could find on the flanks of a 
steep valley, the sub-soil being here shallow.  In this one case, 
the casting was not well dried (3.98)

(2.)  Down.--Largest casting which I could find (consisting chiefly 
of calcareous matter), on extremely poor pasture land at the bottom 
of the valley mentioned under (1.) (3.87)

(3.)  Down.--A large casting, but not of unusual size, from a 
nearly level field, poor pasture, laid down in a grass about 35 
years before (1.22)

(4.)  Down.  Average weight of 11 not large castings ejected on a 
sloping surface on my lawn, after they had suffered some loss of 
weight from being exposed during a considerable length of time to 
rain (0.7)

(5.)  Near Nice in France.--Average weight of 12 castings of 
ordinary dimensions, collected by Dr. King on land which had not 
been mown for a long time and where worms abounded, viz., a lawn 
protected by shrubberies near the sea; soil sandy and calcareous; 
these castings had been exposed for some time to rain, before being 
collected, and must have lost some weight by disintegration, but 
they still retained their form (1.37)

(6.)  The heaviest of the above twelve castings (1.76)

(7.)   Lower Bengal.--Average weight of 22 castings, collected by 
Mr. J. Scott, and stated by him to have been thrown up in the 
course of one or two nights (1.24)

(8.)  The heaviest of the above 22 castings (2.09)

(9.)  Nilgiri Mountains, S. India; average weight of the 5 largest 
castings collected by Dr. King.  They had been exposed to the rain 
of the last monsoon, and must have lost some weight (3.15)

(10.)  The heaviest of the above 5 castings (4.34)


In this table we see that castings which had been ejected at the 
mouth of the same burrow, and which in most cases appeared fresh 
and always retained their vermiform configuration, generally 
exceeded an ounce in weight after being dried, and sometimes nearly 
equalled a quarter of a pound.  On the Nilgiri mountains one 
casting even exceeded this latter weight.  The largest castings in 
England were found on extremely poor pasture-land; and these, as 
far as I have seen, are generally larger than those on land 
producing a rich vegetation.  It would appear that worms have to 
swallow a greater amount of earth on poor than on rich land, in 
order to obtain sufficient nutriment.

With respect to the tower-like castings near Nice (Nos. 5 and 6 in 
the above table), Dr. King often found five or six of them on a 
square foot of surface; and these, judging from their average 
weight, would have weighed together 7.5 ounces; so that the weight 
of those on a square yard would have been 4 lb. 3.5 oz.  Dr. King 
collected, near the close of the year 1872, all the castings which 
still retained their vermiform shape, whether broken down or not, 
from a square foot, in a place abounding with worms, on the summit 
of a bank, where no castings could have rolled down from above.  
These castings must have been ejected, as he judged from their 
appearance in reference to the rainy and dry periods near Nice, 
within the previous five or six months; they weighed 9.5 oz., or 5 
lb. 5.5 oz. per square yard.  After an interval of four months, Dr. 
King collected all the castings subsequently ejected on the same 
square foot of surface, and they weighed 2.5 oz., or 1 lb. 6.5 oz. 
per square yard.  Therefore within about ten months, or we will say 
for safety's sake within a year, 12 oz. of castings were thrown up 
on this one square foot, or 6.75 pounds on the square yard; and 
this would give 14.58 tons per acre.

In a field at the bottom of a valley in the chalk (see No. 2 in the 
foregoing table), a square yard was measured at a spot where very 
large castings abounded; they appeared, however, almost equally 
numerous in a few other places.  These castings, which retained 
perfectly their vermiform shape, were collected; and they weighed 
when partially dried, 1 lb. 13.5 oz.  This field had been rolled 
with a heavy agricultural roller fifty-two days before, and this 
would certainly have flattened every single casting on the land.  
The weather had been very dry for two or three weeks before the day 
of collection, so that not one casting appeared fresh or had been 
recently ejected.  We may therefore assume that those which were 
weighed had been ejected within, we will say, forty days from the 
time when the field was rolled,--that is, twelve days short of the 
whole intervening period.  I had examined the same part of the 
field shortly before it was rolled, and it then abounded with fresh 
castings.  Worms do not work in dry weather during the summer, or 
in winter during severe frosts.  If we assume that they work for 
only half the year--though this is too low an estimate--then the 
worms in this field would eject during the year, 8.387 pounds per 
square yard; or 18.12 tons per acre, assuming the whole surface to 
be equally productive in castings.

In the foregoing cases some of the necessary data had to be 
estimated, but in the two following cases the results are much more 
trustworthy.  A lady, on whose accuracy I can implicitly rely, 
offered to collect during a year all the castings thrown up on two 
separate square yards, near Leith Hill Place, in Surrey.  The 
amount collected was, however, somewhat less than that originally 
ejected by the worms; for, as I have repeatedly observed, a good 
deal of the finest earth is washed away, whenever castings are 
thrown up during or shortly before heavy rain.  Small portions also 
adhered to the surrounding blades of grass, and it required too 
much time to detach every one of them.

On sandy soil, as in the present instance, castings are liable to 
crumble after dry weather, and particles were thus often lost.  The 
lady also occasionally left home for a week or two, and at such 
times the castings must have suffered still greater loss from 
exposure to the weather.  These losses were, however, compensated 
to some extent by the collections having been made on one of the 
squares for four days, and on the other square for two days more 
than the year.

A space was selected (October 9th, 1870) for one of the squares on 
a broad, grass-covered terrace, which had been mowed and swept 
during many years.  It faced the south, but was shaded during part 
of the day by trees.  It had been formed at least a century ago by 
a great accumulation of small and large fragments of sandstone, 
together with some sandy earth, rammed down level.  It is probable 
that it was at first protected by being covered with turf.  This 
terrace, judging from the number of castings on it, was rather 
unfavourable for the existence of worms, in comparison with the 
neighbouring fields and an upper terrace.  It was indeed surprising 
that as many worms could live here as were seen; for on digging a 
hole in this terrace, the black vegetable mould together with the 
turf was only four inches in thickness, beneath which lay the level 
surface of light-coloured sandy soil, with many fragments of 
sandstone.  Before any castings were collected all the previously 
existing ones were carefully removed.  The last day's collection 
was on October 14th, 1871.  The castings were then well dried 
before a fire; and they weighed exactly 3.5 lbs.  This would give 
for an acre of similar land 7.56 tons of dry earth annually ejected 
by worms.

The second square was marked on unenclosed common land, at a height 
of about 700 ft. above the sea, at some little distance from Leith 
Hill Tower.  The surface was clothed with short, fine turf, and had 
never been disturbed by the hand of man.  The spot selected 
appeared neither particularly favourable nor the reverse for worms; 
but I have often noticed that castings are especially abundant on 
common land, and this may, perhaps, be attributed to the poorness 
of the soil.  The vegetable mould was here between three and four 
inches in thickness.  As this spot was at some distance from the 
house where the lady lived, the castings were not collected at such 
short intervals of time as those on the terrace; consequently the 
loss of fine earth during rainy weather must have been greater in 
this than in the last case.  The castings moreover were more sandy, 
and in collecting them during dry weather they sometimes crumbled 
into dust, and much was thus lost.  Therefore it is certain that 
the worms brought up to the surface considerably more earth than 
that which was collected.  The last collection was made on October 
27th, 1871; i.e., 367 days after the square had been marked out and 
the surface cleared of all pre-existing castings.  The collected 
castings, after being well dried, weighed 7.453 pounds; and this 
would give, for an acre of the same kind of land, 16.1 tons of 
annually ejected dry earth.


SUMMARY OF THE FOUR FOREGOING CASES.


(1.)  Castings ejected near Nice within about a year, collected by 
Dr. King on a square foot of surface, calculated to yield per acre 
14.58 tons.

(2.)  Castings ejected during about 40 days on a square yard, in a 
field of poor pasture at the bottom of a large valley in the Chalk, 
calculated to yield annually per acre 18.12 tons.

(3.)  Castings collected from a square yard on an old terrace at 
Leith Hill Place, during 369 days, calculated to yield annually per 
acre 7.56 tons.

(4.)  Castings collected from a square yard on Leith Hill Common 
during 367 days, calculated to yield annually per acre 16.1 tons.


The thickness of the layer of mould, which castings ejected during 
a year would form if uniformly spread out.--As we know, from the 
two last cases in the above summary, the weight of the dried 
castings ejected by worms during a year on a square yard of 
surface, I wished to learn how thick a layer of ordinary mould this 
amount would form if spread uniformly over a square yard.  The dry 
castings were therefore broken into small particles, and whilst 
being placed in a measure were well shaken and pressed down.  Those 
collected on the Terrace amounted to 124.77 cubic inches; and this 
amount, if spread out over a square yard, would make a layer 0.9627 
inch in thickness.  Those collected on the Common amounted to 
197.56 cubic inches, and would make a similar layer 0.1524 inch in 
thickness,

These thicknesses must, however, be corrected, for the triturated 
castings, after being well shaken down and pressed, did not make 
nearly so compact a mass as vegetable mould, though each separate 
particle was very compact.  Yet mould is far from being compact, as 
is shown by the number of air-bubbles which rise up when the 
surface is flooded with water.  It is moreover penetrated by many 
fine roots.  To ascertain approximately by how much ordinary 
vegetable mould would be increased in bulk by being broken up into 
small particles and then dried, a thin oblong block of somewhat 
argillaceous mould (with the turf pared off) was measured before 
being broken up, was well dried and again measured.  The drying 
caused it to shrink by 1/7 of its original bulk, judging from 
exterior measurements alone.  It was then triturated and partly 
reduced to powder, in the same manner as the castings had been 
treated, and its bulk now exceeded (notwithstanding shrinkage from 
drying) by 1/16 that of the original block of damp mould.  
Therefore the above calculated thickness of the layer, formed by 
the castings from the Terrace, after being damped and spread over a 
square yard, would have to be reduced by 1/16; and this will reduce 
the layer to 0.09 of an inch, so that a layer 0.9 inch in thickness 
would be formed in the course of ten years.  On the same principle 
the castings from the Common would make in the course of a single 
year a layer 0.1429 inch, or in the course of 10 years 1.429 inch, 
in thickness.  We may say in round numbers that the thickness in 
the former case would amount to nearly 1 inch, and in the second 
case to nearly 1.5 inch in 10 years.

In order to compare these results with those deduced from the rates 
at which small objects left on the surfaces of grass-fields become 
buried (as described in the early part of this chapter), we will 
give the following summary:-


SUMMARY OF THE THICKNESS OF THE MOULD ACCUMULATED OVER OBJECTS LEFT 
STREWED ON THE SURFACE, IN THE COURSE OF TEN YEARS.


The accumulation of mould during 14.75 years on the surface of a 
dry, sandy, grass-field near Maer Hall, amounted to 2.2 inches in 
10 years.

The accumulation during 21.5 years on a swampy field near Maer 
Hall, amounted to nearly 1.9 inch in 10 years.

The accumulation during 7 years on a very swampy field near Maer 
Hall amounted to 2.1 inches in 10 years.

The accumulation during 29 years, on good, argillaceous pasture-
land over the Chalk at Down, amounted to 2.2 inches in 10 years.

The accumulation during 30 years on the side of a valley over the 
Chalk at Down, the soil being argillaceous, very poor, and only 
just converted into pasture (so that it was for some years 
unfavourable for worms), amounted to 0.83 inch in 10 years.


In these cases (excepting the last) it may be seen that the amount 
of earth brought to the surface during 10 years is somewhat greater 
than that calculated from the castings which were actually weighed.  
This excess may be partly accounted for by the loss which the 
weighed castings had previously undergone through being washed by 
rain, by the adhesion of particles to the blades of the surrounding 
grass, and by their crumbling when dry.  Nor must we overlook other 
agencies which in all ordinary cases add to the amount of mould, 
and which would not be included in the castings that were 
collected, namely, the fine earth brought up to the surface by 
burrowing larvae and insects, especially by ants.  The earth 
brought up by moles generally has a somewhat different appearance 
from vegetable mould; but after a time would not be distinguishable 
from it.  In dry countries, moreover, the wind plays an important 
part in carrying dust from one place to another, and even in 
England it must add to the mould on fields near great roads.  But 
in our country these latter several agencies appear to be of quite 
subordinate importance in comparison with the action of worms.

We have no means of judging how great a weight of earth a single 
full-sized worm ejects during a year.  Hensen estimates that 53,767 
worms exist in an acre of land; but this is founded on the number 
found in gardens, and he believes that only about half as many live 
in corn-fields.  How many live in old pasture land is unknown; but 
if we assume that half the above number, or 26,886 worms live on 
such land, then taking from the previous summary 15 tons as the 
weight of the castings annually thrown up on an acre of land, each 
worm must annually eject 20 ounces.  A full-sized casting at the 
mouth of a single burrow often exceeds, as we have seen, an ounce 
in weight; and it is probable that worms eject more than 20 full-
sized castings during a year.  If they eject annually more than 20 
ounces, we may infer that the worms which live in an acre of 
pasture land must be less than 26,886 in number.

Worms live chiefly in the superficial mould, which is usually from 
4 or 5 to 10 and even 12 inches in thickness; and it is this mould 
which passes over and over again through their bodies and is 
brought to the surface.  But worms occasionally burrow into the 
subsoil to a much greater depth, and on such occasions they bring 
up earth from this greater depth; and this process has gone on for 
countless ages.  Therefore the superficial layer of mould would 
ultimately attain, though at a slower and slower rate, a thickness 
equal to the depth to which worms ever burrow, were there not other 
opposing agencies at work which carry away to a lower level some of 
the finest earth which is continually being brought to the surface 
by worms.  How great a thickness vegetable mould ever attains, I 
have not had good opportunities for observing; but in the next 
chapter, when we consider the burial of ancient buildings, some 
facts will be given on this head.  In the two last chapters we 
shall see that the soil is actually increased, though only to a 
small degree, through the agency of worms; but their chief work is 
to sift the finer from the coarser particles, to mingle the whole 
with vegetable debris, and to saturate it with their intestinal 
secretions.

Finally, no one who considers the facts given in this chapter--on 
the burying of small objects and on the sinking of great stones 
left on the surface--on the vast number of worms which live within 
a moderate extent of ground on the weight of the castings ejected 
from the mouth of the same burrow--on the weight of all the 
castings ejected within a known time on a measured space--will 
hereafter, as I believe, doubt that worms play an important part in 
nature.



CHAPTER IV--THE PART WHICH WORMS HAVE PLAYED IN THE BURIAL OF 
ANCIENT BUILDINGS.



The accumulation of rubbish on the sites of great cities 
independent of the action of worms--The burial of a Roman villa at 
Abinger--The floors and walls penetrated by worms--Subsidence of a 
modern pavement--The buried pavement at Beaulieu Abbey--Roman 
villas at Chedworth and Brading--The remains of the Roman town at 
Silchester--The nature of the debris by which the remains are 
covered--The penetration of the tesselated floors and walls by 
worms--Subsidence of the floors--Thickness of the mould--The old 
Roman city of Wroxeter--Thickness of the mould--Depth of the 
foundations of some of the Buildings--Conclusion.


Archaeologists are probably not aware how much they owe to worms 
for the preservation of many ancient objects.  Coins, gold 
ornaments, stone implements, &c., if dropped on the surface of the 
ground, will infallibly be buried by the castings of worms in a few 
years, and will thus be safely preserved, until the land at some 
future time is turned up.  For instance, many years ago a grass-
field was ploughed on the northern side of the Severn, not far from 
Shrewsbury; and a surprising number of iron arrow-heads were found 
at the bottom of the furrows, which, as Mr. Blakeway, a local 
antiquary, believed, were relics of the battle of Shrewsbury in the 
year 1403, and no doubt had been originally left strewed on the 
battle-field.  In the present chapter I shall show that not only 
implements, &c., are thus preserved, but that the floors and the 
remains of many ancient buildings in England have been buried so 
effectually, in large part through the action of worms, that they 
have been discovered in recent times solely through various 
accidents.  The enormous beds of rubbish, several yards in 
thickness, which underlie many cities, such as Rome, Paris, and 
London, the lower ones being of great antiquity, are not here 
referred to, as they have not been in any way acted on by worms.  
When we consider how much matter is daily brought into a great city 
for building, fuel, clothing and food, and that in old times when 
the roads were bad and the work of the scavenger was neglected, a 
comparatively small amount was carried away, we may agree with Elie 
de Beaumont, who, in discussing this subject, says, "pour une 
voiture de materiaux qui en sort, on y en fait entrer cent." {53}  
Nor should we overlook the effects of fires, the demolition of old 
buildings, and the removal of rubbish to the nearest vacant space,

Abinger, Surrey.--Late in the autumn of 1876, the ground in an old 
farm-yard at this place was dug to a depth of 2 to 2.5 feet, and 
the workmen found various ancient remains.  This led Mr. T. H. 
Farrer of Abinger Hall to have an adjoining ploughed field 
searched.  On a trench being dug, a layer of concrete, still partly 
covered with tesserae (small red tiles), and surrounded on two 
sides by broken-down walls, was soon discovered.  It is believed, 
{54} that this room formed part of the atrium or reception-room of 
a Roman villa.  The walls of two or three other small rooms were 
afterwards discovered.  Many fragments of pottery, other objects, 
and coins of several Roman emperors, dating from 133 to 361, and 
perhaps to 375 A.D., were likewise found.  Also a half-penny of 
George I., 1715.  The presence of this latter coin seems an 
anomaly; but no doubt it was dropped on the ground during the last 
century, and since then there has been ample time for its burial 
under a considerable depth of the castings of worms.  From the 
different dates of the Roman coins we may infer that the building 
was long inhabited.  It was probably ruined and deserted 1400 or 
1500 years ago.

I was present during the commencement of the excavations (August 
20, 1877) and Mr. Farrer had two deep trenches dug at opposite ends 
of the atrium, so that I might examine the nature of the soil near 
the remains.  The field sloped from east to west at an angle of 
about 7 degrees; and one of the two trenches, shown in the 
accompanying section (Fig. 8) was at the upper or eastern end.  The 
diagram is on a scale of 1/20 of an inch to an inch; but the 
trench, which was between 4 and 5 feet broad, and in parts above 5 
feet deep, has necessarily been reduced out of all proportion.  The 
fine mould over the floor of the atrium varied in thickness from 11 
to 16 inches; and on the side of the trench in the section was a 
little over 13 inches.  After the mould had been removed, the floor 
appeared as a whole moderately level; but it sloped in parts at an 
angle of 1 degree, and in one place near the outside at as much as 
8 degrees 30 minutes.  The wall surrounding the pavement was built 
of rough stones, and was 23 inches in thickness where the trench 
was dug.  Its broken summit was here 13 inches, but in another part 
15 inches, beneath the surface of the field, being covered by this 
thickness of mould.  In one spot, however, it rose to within 6 
inches of the surface.  On two sides of the room, where the 
junction of the concrete floor with the bounding walls could be 
carefully examined, there was no crack or separation.  This trench 
afterwards proved to have been dug within an adjoining room (11 ft. 
by 11 ft. 6 in. in size), the existence of which was not even 
suspected whilst I was present.

On the side of the trench farthest from the buried wall (W), the 
mould varied from 9 to 14 inches in thickness; it rested on a mass 
(B) 23 inches thick of blackish earth, including many large stones.  
Beneath this was a thin bed of very black mould (C), then a layer 
of earth full of fragments of mortar (D), and then another thin bed 
(about 3 inches thick) (E) of very black mould, which rested on the 
undisturbed subsoil (F) of firm, yellowish, argillaceous sand.  The 
23-inch bed (B) was probably made ground, as this would have 
brought up the floor of the room to a level with that of the 
atrium.  The two thin beds of black mould at the bottom of the 
trench evidently marked two former land-surfaces.  Outside the 
walls of the northern room, many bones, ashes, oyster-shells, 
broken pottery and an entire pot were subsequently found at a depth 
of 16 inches beneath the surface.

The second trench was dug on the western or lower side of the 
villa:  the mould was here only 6.5 inches in thickness, and it 
rested on a mass of fine earth full of stones, broken tiles and 
fragments of mortar, 34 inches in thickness, beneath which was the 
undisturbed sand.  Most of this earth had probably been washed down 
from the upper part of the field, and the fragments of stones, 
tiles, &c., must have come from the immediately adjoining ruins.

It appears at first sight a surprising fact that this field of 
light sandy soil should have been cultivated and ploughed during 
many years, and that not a vestige of these buildings should have 
been discovered.  No one even suspected that the remains of a Roman 
villa lay hidden close beneath the surface.  But the fact is less 
surprising when it is known that the field, as the bailiff 
believed, had never been ploughed to a greater depth than 4 inches.  
It is certain that when the land was first ploughed, the pavement 
and the surrounding broken walls must have been covered by at least 
4 inches of soil, for otherwise the rotten concrete floor would 
have been scored by the ploughshare, the tesserae torn up, and the 
tops of the old walls knocked down.

When the concrete and tesserae were first cleared over a space of 
14 by 9 ft., the floor which was coated with trodden-down earth 
exhibited no signs of having been penetrated by worms; and although 
the overlying fine mould closely resembled that which in many 
places has certainly been accumulated by worms, yet it seemed 
hardly possible that this mould could have been brought up by worms 
from beneath the apparently sound floor.  It seemed also extremely 
improbable that the thick walls, surrounding the room and still 
united to the concrete, had been undermined by worms, and had thus 
been caused to sink, being afterwards covered up by their castings.  
I therefore at first concluded that all the fine mould above the 
ruins had been washed down from the upper parts of the field; but 
we shall soon see that this conclusion was certainly erroneous, 
though much fine earth is known to be washed down from the upper 
part of the field in its present ploughed state during heavy rains.

Although the concrete floor did not at first appear to have been 
anywhere penetrated by worms, yet by the next morning little cakes 
of the trodden-down earth had been lifted up by worms over the 
mouths of seven burrows, which passed through the softer parts of 
the naked concrete, or between the interstices of the tesserae.  On 
the third morning twenty-five burrows were counted; and by suddenly 
lifting up the little cakes of earth, four worms were seen in the 
act of quickly retreating.  Two castings were thrown up during the 
third night on the floor, and these were of large size.  The season 
was not favourable for the full activity of worms, and the weather 
had lately been hot and dry, so that most of the worms now lived at 
a considerable depth.  In digging the two trenches many open 
burrows and some worms were encountered at between 30 and 40 inches 
beneath the surface; but at a greater depth they became rare.  One 
worm, however, was cut through at 48.5, and another at 51.5 inches 
beneath the surface.  A fresh humus-lined burrow was also met with 
at a depth of 57 and another at 65.5 inches.  At greater depths 
than this, neither burrows nor worms were seen.

As I wished to learn how many worms lived beneath the floor of the 
atrium--a space of about 14 by 9 feet--Mr. Farrer was so kind as to 
make observations for me, during the next seven weeks, by which 
time the worms in the surrounding country were in full activity, 
and were working near the surface.  It is very improbable that 
worms should have migrated from the adjoining field into the small 
space of the atrium, after the superficial mould in which they 
prefer to live, had been removed.  We may therefore conclude that 
the burrows and the castings which were seen here during the 
ensuing seven weeks were the work of the former inhabitants of the 
space.  I will now give a few extracts from Mr. Farrer's notes.

Aug. 26th, 1877; that is, five days after the floor had been 
cleared.  On the previous night there had been some heavy rain, 
which washed the surface clean, and now the mouths of forty burrows 
were counted.  Parts of the concrete were seen to be solid, and had 
never been penetrated by worms, and here the rain-water lodged.

Sept. 5th.--Tracks of worms, made during the previous night, could 
be seen on the surface of the floor, and five or six vermiform 
castings had been thrown up.  These were defaced.

Sept. 12th.--During the last six days, the worms have not been 
active, though many castings have been ejected in the neighbouring 
fields; but on this day the earth was a little raised over the 
mouths of the burrows, or castings were ejected, at ten fresh 
points.  These were defaced.  It should be understood that when a 
fresh burrow is spoken of, this generally means only that an old 
burrow has been re-opened.  Mr. Farrer was repeatedly struck with 
the pertinacity with which the worms re-opened their old burrows, 
even when no earth was ejected from them.  I have often observed 
the same fact, and generally the mouths of the burrows are 
protected by an accumulation of pebbles, sticks or leaves.  Mr. 
Farrer likewise observed that the worms living beneath the floor of 
the atrium often collected coarse grains of sand, and such little 
stones as they could find, round the mouths of their burrows.

Sept. 13th; soft wet weather.  The mouths of the burrows were re-
opened, or castings were ejected, at 31 points; these were all 
defaced.

Sept. 14th; 34 fresh holes or castings; all defaced.

Sept. 15th; 44 fresh holes, only 5 castings; all defaced.

Sept. 18th; 43 fresh holes, 8 castings; all defaced.

The number of castings on the surrounding fields was now very 
large.

Sept. 19th; 40 holes, 8 castings; all defaced.

Sept. 22nd; 43 holes, only a few fresh castings; all defaced.

Sept. 23rd; 44 holes, 8 castings.

Sept. 25th; 50 holes, no record of the number of castings.

Oct. 13th;  61 holes, no record of the number of castings.

After an interval of three years, Mr. Farrer, at my request, again 
looked at the concrete floor, and found the worms still at work.

Knowing what great muscular power worms possess, and seeing how 
soft the concrete was in many parts, I was not surprised at its 
having been penetrated by their burrows; but it is a more 
surprising fact that the mortar between the rough stones of the 
thick walls, surrounding the rooms, was found by Mr. Farrer to have 
been penetrated by worms.  On August 26th, that is, five days after 
the ruins had been exposed, he observed four open burrows on the 
broken summit of the eastern wall (W in Fig. 8); and, on September 
15th, other burrows similarly situated were seen.  It should also 
be noted that in the perpendicular side of the trench (which was 
much deeper than is represented in Fig. 8) three recent burrows 
were seen, which ran obliquely far down beneath the base of the old 
wall.

We thus see that many worms lived beneath the floor and the walls 
of the atrium at the time when the excavations were made; and that 
they afterwards almost daily brought up earth to the surface from a 
considerable depth.  There is not the slightest reason to doubt 
that worms have acted in this manner ever since the period when the 
concrete was sufficiently decayed to allow them to penetrate it; 
and even before that period they would have lived beneath the 
floor, as soon as it became pervious to rain, so that the soil 
beneath was kept damp.  The floor and the walls must therefore have 
been continually undermined; and fine earth must have been heaped 
on them during many centuries, perhaps for a thousand years.  If 
the burrows beneath the floor and walls, which it is probable were 
formerly as numerous as they now are, had not collapsed in the 
course of time in the manner formerly explained, the underlying 
earth would have been riddled with passages like a sponge; and as 
this was not the case, we may feel sure that they have collapsed.  
The inevitable result of such collapsing during successive 
centuries, will have been the slow subsidence of the floor and of 
the walls, and their burial beneath the accumulated worm-castings.  
The subsidence of a floor, whilst it still remains nearly 
horizontal, may at first appear improbable; but the case presents 
no more real difficulty than that of loose objects strewed on the 
surface of a field, which, as we have seen, become buried several 
inches beneath the surface in the course of a few years, though 
still forming a horizontal layer parallel to the surface.  The 
burial of the paved and level path on my lawn, which took place 
under my own observation, is an analogous case.  Even those parts 
of the concrete floor which the worms could not penetrate would 
almost certainly have been undermined, and would have sunk, like 
the great stones at Leith Hill Place and Stonehenge, for the soil 
would have been damp beneath them.  But the rate of sinking of the 
different parts would not have been quite equal, and the floor was 
not quite level.  The foundations of the boundary walls lie, as 
shown in the section, at a very small depth beneath the surface; 
they would therefore have tended to subside at nearly the same rate 
as the floor.  But this would not have occurred if the foundations 
had been deep, as in the case of some other Roman ruins presently 
to be described.

Finally, we may infer that a large part of the fine vegetable 
mould, which covered the floor and the broken-down walls of this 
villa, in some places to a thickness of 16 inches, was brought up 
from below by worms.  From facts hereafter to be given there can be 
no doubt that some of the finest earth thus brought up will have 
been washed down the sloping surface of the field during every 
heavy shower of rain.  If this had not occurred a greater amount of 
mould would have accumulated over the ruins than that now present.  
But beside the castings of worms and some earth brought up by 
insects, and some accumulation of dust, much fine earth will have 
been washed over the ruins from the upper parts of the field, since 
it has been under cultivation; and from over the ruins to the lower 
parts of the slope; the present thickness of the mould being the 
resultant of these several agencies.


I may here append a modern instance of the sinking of a pavement, 
communicated to me in 1871 by Mr. Ramsay, Director of the 
Geological Survey of England.  A passage without a roof, 7 feet in 
length by 3 feet 2 inches in width, led from his house into the 
garden, and was paved with slabs of Portland stone.  Several of 
these slabs were 16 inches square, others larger, and some a little 
smaller.  This pavement had subsided about 3 inches along the 
middle of the passage, and two inches on each side, as could be 
seen by the lines of cement by which the slabs had been originally 
joined to the walls.  The pavement had thus become slightly concave 
along the middle; but there was no subsidence at the end close to 
the house.  Mr. Ramsay could not account for this sinking, until he 
observed that castings of black mould were frequently ejected along 
the lines of junction between the slabs; and these castings were 
regularly swept away.  The several lines of junction, including 
those with the lateral walls, were altogether 39 feet 2 inches in 
length.  The pavement did not present the appearance of ever having 
been renewed, and the house was believed to have been built about 
eighty-seven years ago.  Considering all these circumstances, Mr. 
Ramsay does not doubt that the earth brought up by the worms since 
the pavement was first laid down, or rather since the decay of the 
mortar allowed the worms to burrow through it, and therefore within 
a much shorter time than the eighty-seven years, has sufficed to 
cause the sinking of the pavement to the above amount, except close 
to the house, where the ground beneath would have been kept nearly 
dry.

Beaulieu Abbey, Hampshire.--This abbey was destroyed by Henry 
VIII., and there now remains only a portion of the southern aisle-
wall.  It is believed that the king had most of the stones carried 
away for building a castle; and it is certain that they have been 
removed.  The positions of the nave and transepts were ascertained 
not long ago by the foundations having been found; and the place is 
now marked by stones let into the ground.  Where the abbey formerly 
stood, there now extends a smooth grass-covered surface, which 
resembles in all respects the rest of the field.  The guardian, a 
very old man, said the surface had never been levelled in his time.  
In the year 1853, the Duke of Buccleuch had three holes dug in the 
turf within a few yards of one another, at the western end of the 
nave; and the old tesselated pavement of the abbey was thus 
discovered.  These holes were afterwards surrounded by brickwork, 
and protected by trap-doors, so that the pavement might be readily 
inspected and preserved.  When my son William examined the place on 
January 5, 1872, he found that the pavement in the three holes lay 
at depths of 6.75, 10 and 11.5 inches beneath the surrounding turf-
covered surface.  The old guardian asserted that he was often 
forced to remove worm-castings from the pavement; and that he had 
done so about six months before.  My son collected all from one of 
the holes, the area of which was 5.32 square feet, and they weighed 
7.97 ounces.  Assuming that this amount had accumulated in six 
months, the accumulation during a year on a square yard would be 
1.68 pounds, which, though a large amount, is very small compared 
with what, as we have seen, is often ejected on fields and commons.  
When I visited the abbey on June 22, 1877, the old man said that he 
had cleared out the holes about a month before, but a good many 
castings had since been ejected.  I suspect that he imagined that 
he swept the pavements oftener than he really did, for the 
conditions were in several respects very unfavourable for the 
accumulation of even a moderate amount of castings.  The tiles are 
rather large, viz., about 5.5 inches square, and the mortar between 
them was in most places sound, so that the worms were able to bring 
up earth from below only at certain points.  The tiles rested on a 
bed of concrete, and the castings in consequence consisted in large 
part (viz., in the proportion of 19 to 33) of particles of mortar, 
grains of sand, little fragments of rock, bricks or tile; and such 
substances could hardly be agreeable, and certainly not nutritious, 
to worms.

My son dug holes in several places within the former walls of the 
abbey, at a distance of several yards from the above described 
bricked squares.  He did not find any tiles, though these are known 
to occur in some other parts, but he came in one spot to concrete 
on which tiles had once rested.  The fine mould beneath the turf on 
the sides of the several holes, varied in thickness from only 2 to 
2.75 inches, and this rested on a layer from 8.75 to above 11 
inches in thickness, consisting of fragments of mortar and stone-
rubbish with the interstices compactly filled up with black mould.  
In the surrounding field, at a distance of 20 yards from the abbey, 
the fine vegetable mould was 11 inches thick.

We may conclude from these facts that when the abbey was destroyed 
and the stones removed, a layer of rubbish was left over the whole 
surface, and that as soon as the worms were able to penetrate the 
decayed concrete and the joints between the tiles, they slowly 
filled up the interstices in the overlying rubbish with their 
castings, which were afterwards accumulated to a thickness of 
nearly three inches over the whole surface.  If we add to this 
latter amount the mould between the fragments of stones, some five 
or six inches of mould must have been brought up from beneath the 
concrete or tiles.  The concrete or tiles will consequently have 
subsided to nearly this amount.  The bases of the columns of the 
aisles are now buried beneath mould and turf.  It is not probable 
that they can have been undermined by worms, for their foundations 
would no doubt have been laid at a considerable depth.  If they 
have not subsided, the stones of which the columns were constructed 
must have been removed from beneath the former level of the floor.

Chedworth, Gloucestershire.--The remains of a large Roman villa 
were discovered here in 1866, on ground which had been covered with 
wood from time immemorial.  No suspicion seems ever to have been 
entertained that ancient buildings lay buried here, until a 
gamekeeper, in digging for rabbits, encountered some remains. {55}  
But subsequently the tops of some stone walls were detected in 
parts of the wood, projecting a little above the surface of the 
ground.  Most of the coins found here belonged to Constans (who 
died 350 A.D.) and the Constantine family.  My sons Francis and 
Horace visited the place in November 1877, for the sake of 
ascertaining what part worms may have played in the burial of these 
extensive remains.  But the circumstances were not favourable for 
this object, as the ruins are surrounded on three sides by rather 
steep banks, down which earth is washed during rainy weather.  
Moreover most of the old rooms have been covered with roofs, for 
the protection of the elegant tesselated pavements.

A few facts may, however, be given on the thickness of the soil 
over these ruins.  Close outside the northern rooms there is a 
broken wall, the summit of which was covered by 5 inches of black 
mould; and in a hole dug on the outer side of this wall, where the 
ground had never before been disturbed, black mould, full of 
stones, 26 inches in thickness, was found, resting on the 
undisturbed sub-soil of yellow clay.  At a depth of 22 inches from 
the surface a pig's jaw and a fragment of a tile were found.  When 
the excavations were first made, some large trees grew over the 
ruins; and the stump of one has been left directly over a party-
wall near the bath-room, for the sake of showing the thickness of 
the superincumbent soil, which was here 38 inches.  In one small 
room, which, after being cleared out, had not been roofed over, my 
sons observed the hole of a worm passing through the rotten 
concrete, and a living worm was found within the concrete.  In 
another open room worm-castings were seen on the floor, over which 
some earth had by this means been deposited, and here grass now 
grew.

Brading, Isle of Wight.--A fine Roman villa was discovered here in 
1880; and by the end of October no less than 18 chambers had been 
more or less cleared.  A coin dated 337 A.D.  was found.  My son 
William visited the place before the excavations were completed; 
and he informs me that most of the floors were at first covered 
with much rubbish and fallen stones, having their interstices 
completely filled up with mould, abounding, as the workmen said, 
with worms, above which there was mould without any stones.  The 
whole mass was in most places from 3 to above 4 ft. in thickness.  
In one very large room the overlying earth was only 2 ft. 6 in. 
thick; and after this had been removed, so many castings were 
thrown up between the tiles that the surface had to be almost daily 
swept.  Most of the floors were fairly level.  The tops of the 
broken-down walls were covered in some places by only 4 or 5 inches 
of soil, so that they were occasionally struck by the plough, but 
in other places they were covered by from 13 to 18 inches of soil.  
It is not probable that these walls could have been undermined by 
worms and subsided, as they rested on a foundation of very hard red 
sand, into which worms could hardly burrow.  The mortar, however, 
between the stones of the walls of a hypocaust was found by my son 
to have been penetrated by many worm-burrows.  The remains of this 
villa stand on land which slopes at an angle of about 3 degrees; 
and the land appears to have been long cultivated.  Therefore no 
doubt a considerable quantity of fine earth has been washed down 
from the upper parts of the field, and has largely aided in the 
burial of these remains.

Silchester, Hampshire.--The ruins of this small Roman town have 
been better preserved than any other remains of the kind in 
England.  A broken wall, in most parts from 15 to 18 feet in height 
and about 1.5 mile in compass, now surrounds a space of about 100 
acres of cultivated land, on which a farm-house and a church stand. 
{56}  Formerly, when the weather was dry, the lines of the buried 
walls could be traced by the appearance of the crops; and recently 
very extensive excavations have been undertaken by the Duke of 
Wellington, under the superintendence of the late Rev. J. G. Joyce, 
by which means many large buildings have been discovered.  Mr. 
Joyce made careful coloured sections, and measured the thickness of 
each bed of rubbish, whilst the excavations were in progress; and 
he has had the kindness to send me copies of several of them.  When 
my sons Francis and Horace visited these ruins, he accompanied 
them, and added his notes to theirs.

Mr. Joyce estimates that the town was inhabited by the Romans for 
about three centuries; and no doubt much matter must have 
accumulated within the walls during this long period.  It appears 
to have been destroyed by fire, and most of the stones used in the 
buildings have since been carried away.  These circumstances are 
unfavourable for ascertaining the part which worms have played in 
the burial of the ruins; but as careful sections of the rubbish 
overlying an ancient town have seldom or never before been made in 
England, I will give copies of the most characteristic portions of 
some of those made by Mr. Joyce.  They are of too great length to 
be here introduced entire.

An east and west section, 30 ft. in length, was made across a room 
in the Basilica, now called the Hall of the Merchants (Fig. 9).  
The hard concrete floor, still covered here and there with 
tesserae, was found at 3 ft. beneath the surface of the field, 
which was here level.  On the floor there were two large piles of 
charred wood, one alone of which is shown in the part of the 
section here given.  This pile was covered by a thin white layer of 
decayed stucco or plaster, above which was a mass, presenting a 
singularly disturbed appearance, of broken tiles, mortar, rubbish 
and fine gravel, together 27 inches in thickness.  Mr. Joyce 
believes that the gravel was used in making the mortar or concrete, 
which has since decayed, some of the lime probably having been 
dissolved.  The disturbed state of the rubbish may have been due to 
its having been searched for building stones.  This bed was capped 
by fine vegetable mould, 9 inches in thickness.  From these facts 
we may conclude that the Hall was burnt down, and that much rubbish 
fell on the floor, through and from which the worms slowly brought 
up the mould, now forming the surface of the level field.

A section across the middle of another hall in the Basilica, 32 
feet 6 inches in length, called the AErarium, is shown in Fig. 10.  
It appears that we have here evidence of two fires, separated by an 
interval of time, during which the 6 inches of "mortar and concrete 
with broken tiles" was accumulated.  Beneath one of the layers of 
charred wood, a valuable relic, a bronze eagle, was found; and this 
shows that the soldiers must have deserted the place in a panic.  
Owing to the death of Mr. Joyce, I have not been able to ascertain 
beneath which of the two layers the eagle was found.  The bed of 
rubble overlying the undisturbed gravel originally formed, as I 
suppose, the floor, for it stands on a level with that of a 
corridor, outside the walls of the Hall; but the corridor is not 
shown in the section as here given.  The vegetable mould was 16 
inches thick in the thickest part; and the depth from the surface 
of the field, clothed with herbage, to the undisturbed gravel, was 
40 inches.

The section shown in Fig. 11 represents an excavation made in the 
middle of the town, and is here introduced because the bed of "rich 
mould" attained, according to Mr. Joyce, the unusual thickness of 
20 inches.  Gravel lay at the depth of 48 inches from the surface; 
but it was not ascertained whether this was in its natural state, 
or had been brought here and had been rammed down, as occurs in 
some other places.

The section shown in Fig. 12 was taken in the centre of the 
Basilica, and though it was 5 feet in depth, the natural sub-soil 
was not reached.  The bed marked "concrete" was probably at one 
time a floor; and the beds beneath seem to be the remnants of more 
ancient buildings.  The vegetable mould was here only 9 inches 
thick.  In some other sections, not copied, we likewise have 
evidence of buildings having been erected over the ruins of older 
ones.  In one case there was a layer of yellow clay of very unequal 
thickness between two beds of debris, the lower one of which rested 
on a floor with tesserae.  The ancient broken walls appear to have 
been sometimes roughly cut down to a uniform level, so as to serve 
as the foundations for a temporary building; and Mr. Joyce suspects 
that some of these buildings were wattled sheds, plastered with 
clay, which would account for the above-mentioned layer of clay.

Turning now to the points which more immediately concern us.  Worm-
castings were observed on the floors of several of the rooms, in 
one of which the tesselation was unusually perfect.  The tesserae 
here consisted of little cubes of hard sandstone of about 1 inch, 
several of which were loose or projected slightly above the general 
level.  One or occasionally two open worm-burrows were found 
beneath all the loose tesserae.  Worms have also penetrated the old 
walls of these ruins.  A wall, which had just been exposed to view 
during the excavations then in progress, was examined; it was built 
of large flints, and was 18 inches in thickness.  It appeared 
sound, but when the soil was removed from beneath, the mortar in 
the lower part was found to be so much decayed that the flints fell 
apart from their own weight.  Here, in the middle of the wall, at a 
depth of 29 inches beneath the old floor and of 49.5 inches beneath 
the surface of the field, a living worm was found, and the mortar 
was penetrated by several burrows.

A second wall was exposed to view for the first time, and an open 
burrow was seen on its broken summit.  By separating the flints 
this burrow was traced far down in the interior of the wall; but as 
some of the flints cohered firmly, the whole mass was disturbed in 
pulling down the wall, and the burrow could not be traced to the 
bottom.  The foundations of a third wall, which appeared quite 
sound, lay at a depth of 4 feet beneath one of the floors, and of 
course at a considerably greater depth beneath the level of the 
ground.  A large flint was wrenched out of the wall at about a foot 
from the base, and this required much force, as the mortar was 
sound; but behind the flint in the middle of the wall, the mortar 
was friable, and here there were worm-burrows.  Mr. Joyce and my 
sons were surprised at the blackness of the mortar in this and in 
several other cases, and at the presence of mould in the interior 
of the walls.  Some may have been placed there by the old builders 
instead of mortar; but we should remember that worms line their 
burrows with black humus.  Moreover open spaces would almost 
certainly have been occasionally left between the large irregular 
flints; and these spaces, we may feel sure, would be filled up by 
the worms with their castings, as soon as they were able to 
penetrate the wall.  Rain-water, oozing down the burrows would also 
carry fine dark-coloured particles into every crevice.  Mr. Joyce 
was at first very sceptical about the amount of work which I 
attributed to worms; but he ends his notes with reference to the 
last-mentioned wall by saying, "This case caused me more surprise 
and brought more conviction to me than any other.  I should have 
said, and did say, that it was quite impossible such a wall could 
have been penetrated by earth-worms."

In almost all the rooms the pavement has sunk considerably, 
especially towards the middle; and this is shown in the three 
following sections.  The measurements were made by stretching a 
string tightly and horizontally over the floor.  The section, Fig. 
13, was taken from north to south across a room, 18 feet 4 inches 
in length, with a nearly perfect pavement, next to the "Red Wooden 
Hut."  In the northern half, the subsidence amounted to 5.75 inches 
beneath the level of the floor as it now stands close to the walls; 
and it was greater in the northern than in the southern half; but, 
according to Mr. Joyce, the entire pavement has obviously subsided.  
In several places, the tesserae appeared as if drawn a little away 
from the walls; whilst in other places they were still in close 
contact with them.

In Fig. 14, we see a section across the paved floor of the southern 
corridor or ambulatory of a quadrangle, in an excavation made near 
"The Spring."  The floor is 7 feet 9 inches wide, and the broken-
down walls now project only 0.75 of an inch above its level.  The 
field, which was in pasture, here sloped from north to south, at an 
angle of 30 degrees, 40 seconds.  The nature of the ground at some 
little distance on each side of the corridor is shown in the 
section.  It consisted of earth full of stones and other debris, 
capped with dark vegetable mould which was thicker on the lower or 
southern than on the northern side.  The pavement was nearly level 
along lines parallel to the side-walls, but had sunk in the middle 
as much as 7.75 inches.

A small room at no great distance from that represented in Fig. 13, 
had been enlarged by the Roman occupier on the southern side, by an 
addition of 5 feet 4 inches in breadth.  For this purpose the 
southern wall of the house had been pulled down, but the 
foundations of the old wall had been left buried at a little depth 
beneath the pavement of the enlarged room.  Mr. Joyce believes that 
this buried wall must have been built before the reign of Claudius 
II., who died 270 A.D.  We see in the accompanying section, Fig. 
15, that the tesselated pavement has subsided to a less degree over 
the buried wall than elsewhere; so that a slight convexity or 
protuberance here stretched in a straight line across the room.  
This led to a hole being dug, and the buried wall was thus 
discovered.

We see in these three sections, and in several others not given, 
that the old pavements have sunk or sagged considerably.  Mr. Joyce 
formerly attributed this sinking solely to the slow settling of the 
ground.  That there has been some settling is highly probable, and 
it may be seen in Fig. 15 that the pavement for a width of 5 feet 
over the southern enlargement of the room, which must have been 
built on fresh ground, has sunk a little more than on the old 
northern side.  But this sinking may possibly have had no 
connection with the enlargement of the room; for in Fig. 13 one 
half of the pavement has subsided more than the other half without 
any assignable cause.  In a bricked passage to Mr. Joyce's own 
house, laid down only about six years ago, the same kind of sinking 
has occurred as in the ancient buildings.  Nevertheless it does not 
appear probable that the whole amount of sinking can be thus 
accounted for.  The Roman builders excavated the ground to an 
unusual depth for the foundations of their walls, which were thick 
and solid; it is therefore hardly credible that they should have 
been careless about the solidity of the bed on which their 
tesselated and often ornamented pavements were laid.  The sinking 
must, as it appears to me, be attributed in chief part to the 
pavement having been undermined by worms, which we know are still 
at work.  Even Mr. Joyce at last admitted that this could not have 
failed to have produced a considerable effect.  Thus also the large 
quantity of fine mould overlying the pavements can be accounted 
for, the presence of which would otherwise be inexplicable.  My 
sons noticed that in one room in which the pavement had sagged very 
little, there was an unusually small amount of overlying mould.

As the foundations of the walls generally lie at a considerable 
depth, they will either have not subsided at all through the 
undermining action of worms, or they will have subsided much less 
than the floor.  This latter result would follow from worms not 
often working deep down beneath the foundations; but more 
especially from the walls not yielding when penetrated by worms, 
whereas the successively formed burrows in a mass of earth, equal 
to one of the walls in depth and thickness, would have collapsed 
many times since the desertion of the ruins, and would consequently 
have shrunk or subsided.  As the walls cannot have sunk much or at 
all, the immediately adjoining pavement from adhering to them will 
have been prevented from subsiding; and thus the present curvature 
of the pavement is intelligible.

The circumstance which has surprised me most with respect to 
Silchester is that during the many centuries which have elapsed 
since the old buildings were deserted, the vegetable mould has not 
accumulated over them to a greater thickness than that here 
observed.  In most places it is only about 9 inches in thickness, 
but in some places 12 or even more inches.  In Fig. 11, it is given 
as 20 inches, but this section was drawn by Mr. Joyce before his 
attention was particularly called to this subject.  The land 
enclosed within the old walls is described as sloping slightly to 
the south; but there are parts which, according to Mr. Joyce, are 
nearly level, and it appears that the mould is here generally 
thicker than elsewhere.  The surface slopes in other parts from 
west to east, and Mr. Joyce describes one floor as covered at the 
western end by rubbish and mould to a thickness of 28.5 inches, and 
at the eastern end by a thickness of only 11.5 inches.  A very 
slight slope suffices to cause recent castings to flow downwards 
during heavy rain, and thus much earth will ultimately reach the 
neighbouring rills and streams and be carried away.  By this means, 
the absence of very thick beds of mould over these ancient ruins 
may, as I believe, be explained.  Moreover most of the land here 
has long been ploughed, and this would greatly aid the washing away 
of the finer earth during rainy weather.

The nature of the beds immediately beneath the vegetable mould in 
some of the sections is rather perplexing.  We see, for instance, 
in the section of an excavation in a grass meadow (Fig. 14), which 
sloped from north to south at an angle of 30 degrees 40 seconds, 
that the mould on the upper side is only six inches and on the 
lower side nine inches in thickness.  But this mould lies on a mass 
(25.5 inches in thickness on the upper side) "of dark brown mould," 
as described by Mr. Joyce, "thickly interspersed with small pebbles 
and bits of tiles, which present a corroded or worn appearance.  
The state of this dark-coloured earth is like that of a field which 
has long been ploughed, for the earth thus becomes intermingled 
with stones and fragments of all kinds which have been much exposed 
to the weather.  If during the course of many centuries this grass 
meadow and the other now cultivated fields have been at times 
ploughed, and at other times left as pasture, the nature of the 
ground in the above section is rendered intelligible.  For worms 
will continually have brought up fine earth from below, which will 
have been stirred up by the plough whenever the land was 
cultivated.  But after a time a greater thickness of fine earth 
will thus have been accumulated than could be reached by the 
plough; and a bed like the 25.5-inch mass, in Fig. 14, will have 
been formed beneath the superficial mould, which latter will have 
been brought to the surface within more recent times, and have been 
well sifted by the worms.

Wroxeter, Shropshire. --The old Roman city of Uriconium was founded 
in the early part of the second century, if not before this date; 
and it was destroyed, according to Mr. Wright, probably between the 
middle of the fourth and fifth century.  The inhabitants were 
massacred, and skeletons of women were found in the hypocausts.  
Before the year 1859, the sole remnant of the city above ground, 
was a portion of a massive wall about 20 ft. in height.  The 
surrounding land undulates slightly, and has long been under 
cultivation.  It had been noticed that the corn-crops ripened 
prematurely in certain narrow lines, and that the snow remained 
unmelted in certain places longer than in others.  These 
appearances led, as I was informed, to extensive excavations being 
undertaken.  The foundations of many large buildings and several 
streets have thus been exposed to view.  The space enclosed within 
the old walls is an irregular oval, about 1 mile in length.  Many 
of the stones or bricks used in the buildings must have been 
carried away; but the hypocausts, baths, and other underground 
buildings were found tolerably perfect, being filled with stones, 
broken tiles, rubbish and soil.  The old floors of various rooms 
were covered with rubble.  As I was anxious to know how thick the 
mantle of mould and rubbish was, which had so long concealed these 
ruins, I applied to Dr. H. Johnson, who had superintended the 
excavations; and he, with the greatest kindness, twice visited the 
place to examine it in reference to my questions, and had many 
trenches dug in four fields which had hitherto been undisturbed.  
The results of his observations are given in the following Table.  
He also sent me specimens of the mould, and answered, as far as he 
could, all my questions.


MEASUREMENTS BY DR. H. JOHNSON OF THE THICKNESS OF THE VEGETABLE 
MOULD OVER THE ROMAN RUINS AT WROXETER.


Trenches dug in a field called "Old Works."

(Thickness of mould in inches shown in parenthesis--DP.)

1.  At a depth of 36 inches undisturbed sand was reached (20)

2.  At a depth of 33 inches concrete was reached (21)

3. At a depth of 9 inches concrete was reached (9)

Trenches dug in a field called "Shop Leasows;" this is the highest 
field within the old walls, and slopes down from a sub-central 
point on all sides at about an angle of 2 degrees.

4.  Summit of field, trench 45 inches deep (40)

5.  Close to summit of field, trench 36 inches deep (26)

6.  Close to summit of field, trench 28 inches deep (28)

7.  Near summit of field, trench 36 inches deep (24)

8.  Near summit of field, trench at one end 39 inches deep; the 
mould here graduated into the underlying undisturbed sand, and its 
thickness (24 inches) is somewhat arbitrary.  At the other end of 
the trench, a causeway was encountered at a depth of only 7 inches, 
and the mould was here only 7 inches thick (24)

9.  Trench close to the last, 28 inches in depth (24)

10.  Lower part of same field, trench 30 inches deep (15)

11.  Lower part of same field, trench 31 inches deep (17)

12.  Lower part of same field, trench 36 inches deep, at which 
depth undisturbed sand was reached (28)

13.  In another part of same field, trench 9.5 inches deep stopped 
by concrete (9.5)

14.  In another part of same field, trench 9 inches deep, stopped 
by concrete (9)

15.  In another part of the same field, trench 24 inches deep, when 
sand was reached (16)

16.  In another part of same field, trench 30 inches deep, when 
stones were reached; at one end of the trench mould 12 inches, at 
the other end 14 inches thick (13)

Small field between "Old Works" and "Shop Leasows," I believe 
nearly as high as the upper part of the latter field.

17.  Trench 26 inches deep (24)

18.  Trench 10 inches deep, and then came upon a causeway (10)

19.  Trench 34 inches deep (30)

20. Trench 31 inches deep (31)

Field on the western side of the space enclosed within the old 
walls.

21.  Trench 28 inches deep, when undisturbed sand was reached (16)

22.  Trench 29 inches deep, when undisturbed sand was reached (15)

23.  Trench 14 inches deep, and then came upon a building (14)


Dr. Johnson distinguished as mould the earth which differed, more 
or less abruptly, in its dark colour and in its texture from the 
underlying sand or rubble.  In the specimens sent to me, the mould 
resembled that which lies immediately beneath the turf in old 
pasture-land, excepting that it often contained small stones, too 
large to have passed through the bodies of worms.  But the trenches 
above described were dug in fields, none of which were in pasture, 
and all had been long cultivated.  Bearing in mind the remarks made 
in reference to Silchester on the effects of long-continued 
culture, combined with the action of worms in bringing up the finer 
particles to the surface, the mould, as so designated by Dr. 
Johnson, seems fairly well to deserve its name.  Its thickness, 
where there was no causeway, floor or walls beneath, was greater 
than has been elsewhere observed, namely, in many places above 2 
ft., and in one spot above 3 ft.  The mould was thickest on and 
close to the nearly level summit of the field called "Shop 
Leasows," and in a small adjoining field, which, as I believe, is 
of nearly the same height.  One side of the former field slopes at 
an angle of rather above 2 degrees, and I should have expected that 
the mould, from being washed down during heavy rain, would have 
been thicker in the lower than in the upper part; but this was not 
the case in two out of the three trenches here dug.

In many places, where streets ran beneath the surface, or where old 
buildings stood, the mould was only 8 inches in thickness; and Dr.  
Johnson was surprised that in ploughing the land, the ruins had 
never been struck by the plough as far as he had heard.  He thinks 
that when the land was first cultivated the old walls were perhaps 
intentionally pulled down, and that hollow places were filled up.  
This may have been the case; but if after the desertion of the city 
the land was left for many centuries uncultivated, worms would have 
brought up enough fine earth to have covered the ruins completely; 
that is if they had subsided from having been undermined.  The 
foundations of some of the walls, for instance those of the portion 
still standing about 20 feet above the ground, and those of the 
marketplace, lie at the extraordinary depth of 14 feet; but it is 
highly improbable that the foundations were generally so deep.  The 
mortar employed in the buildings must have been excellent, for it 
is still in parts extremely hard.  Wherever walls of any height 
have been exposed to view, they are, as Dr.  Johnson believes, 
still perpendicular.  The walls with such deep foundations cannot 
have been undermined by worms, and therefore cannot have subsided, 
as appears to have occurred at Abinger and Silchester.  Hence it is 
very difficult to account for their being now completely covered 
with earth; but how much of this covering consists of vegetable 
mould and how much of rubble I do not know.  The market-place, with 
the foundations at a depth of 14 feet, was covered up, as Dr.  
Johnson believes, by between 6 and 24 inches of earth.  The tops of 
the broken-down walls of a caldarium or bath, 9 feet in depth, were 
likewise covered up with nearly 2 feet of earth.  The summit of an 
arch, leading into an ash-pit 7 feet in depth, was covered up with 
not more than 8 inches of earth.  Whenever a building which has not 
subsided is covered with earth, we must suppose, either that the 
upper layers of stone have been at some time carried away by man, 
or that earth has since been washed down during heavy rain, or 
blown down during storms, from the adjoining land; and this would 
be especially apt to occur where the land has long been cultivated.  
In the above cases the adjoining land is somewhat higher than the 
three specified sites, as far as I can judge by maps and from 
information given me by Dr.  Johnson.  If; however, a great pile of 
broken stones, mortar, plaster, timber and ashes fell over the 
remains of any building, their disintegration in the course of 
time, and the sifting action of worms, would ultimately conceal the 
whole beneath fine earth.

Conclusion. --The cases given in this chapter show that worms have 
played a considerable part in the burial and concealment of several 
Roman and other old buildings in England; but no doubt the washing 
down of soil from the neighbouring higher lands, and the deposition 
of dust, have together aided largely in the work of concealment.  
Dust would be apt to accumulate wherever old broken-down walls 
projected a little above the then existing surface and thus 
afforded some shelter.  The floors of the old rooms, halls and 
passages have generally sunk, partly from the settling of the 
ground, but chiefly from having been undermined by worms; and the 
sinking has commonly been greater in the middle than near the 
walls.  The walls themselves, whenever their foundations do not lie 
at a great depth, have been penetrated and undermined by worms, and 
have consequently subsided.  The unequal subsidence thus caused, 
probably explains the great cracks which may be seen in many 
ancient walls, as well as their inclination from the perpendicular.



CHAPTER V--THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.



Evidence of the amount of denudation which the land has undergone--
Sub-aerial denudation--The deposition of dust--Vegetable mould, its 
dark colour and fine texture largely due to the action of worms--
The disintegration of rocks by the humus-acids --Similar acids 
apparently generated within the bodies of worms--The action of 
these acids facilitated by the continued movement of the particles 
of earth--A thick bed of mould checks the disintegration of the 
underlying soil and rocks.  Particles of stone worn or triturated 
in the gizzards of worms--Swallowed stones serve as mill-stones--
The levigated state of the castings--Fragments of brick in the 
castings over ancient buildings well rounded.  The triturating 
power of worms not quite insignificant under a geological point of 
view.


No one doubts that our world at one time consisted of crystalline 
rocks, and that it is to their disintegration through the action of 
air, water, changes of temperature, rivers, waves of the sea, 
earthquakes and volcanic outbursts, that we owe our sedimentary 
formations.  These after being consolidated and sometimes 
recrystallized, have often been again disintegrated.  Denudation 
means the removal of such disintegrated matter to a lower level.  
Of the many striking results due to the modern progress of geology 
there are hardly any more striking than those which relate to 
denudation.  It was long ago seen that there must have been an 
immense amount of denudation; but until the successive formations 
were carefully mapped and measured, no one fully realised how great 
was the amount.  One of the first and most remarkable memoirs ever 
published on this subject was that by Ramsay, {57} who in 1846 
showed that in Wales from 9000 to 11,000 feet in thickness of solid 
rock had been stripped off large tracks of country.  Perhaps the 
plainest evidence of great denudation is afforded by faults or 
cracks, which extend for many miles across certain districts, with 
the strata on one side raised even ten thousand feet above the 
corresponding strata on the opposite side; and yet there is not a 
vestige of this gigantic displacement visible on the surface of the 
land.  A huge pile of rock has been planed away on one side and not 
a remnant left.

Until the last twenty or thirty years, most geologists thought that 
the waves of the sea were the chief agents in the work of 
denudation; but we may now feel sure that air and rain, aided by 
streams and rivers, are much more powerful agents,--that is if we 
consider the whole area of the land.  The long lines of escarpment 
which stretch across several parts of England were formerly 
considered to be undoubtedly ancient coast-lines; but we now know 
that they stand up above the general surface merely from resisting 
air, rain and frost better than the adjoining formations.  It has 
rarely been the good fortune of a geologist to bring conviction to 
the minds of his fellow-workers on a disputed point by a single 
memoir; but Mr. Whitaker, of the Geological Survey of England, was 
so fortunate when, in 1867, he published his paper "On sub-aerial 
Denudation, and on Cliffs and Escarpments of the Chalk." {58}  
Before this paper appeared, Mr. A. Tylor had adduced important 
evidence on sub-aerial denudation, by showing that the amount of 
matter brought down by rivers must infallibly lower the level of 
their drainage basins by many feet in no immense lapse of time.  
This line of argument has since been followed up in the most 
interesting manner by Archibald Geikie, Croll and others, in a 
series of valuable memoirs. {59}  For the sake of those who have 
never attended to this subject, a single instance may be here 
given, namely, that of the Mississippi, which is chosen because the 
amount of sediment brought down by this great river has been 
investigated with especial care by order of the United States 
Government.  The result is, as Mr. Croll shows, that the mean level 
of its enormous area of drainage must be lowered 1/4566 of a foot 
annually, or 1 foot in 4566 years.  Consequently, taking the best 
estimate of the mean height of the North American continent, viz. 
748 feet, and looking to the future, the whole of the great 
Mississippi basin will be washed away, and "brought down to the 
sea-level in less than 4,500,000 years, if no elevation of the land 
takes place."  Some rivers carry down much more sediment relatively 
to their size, and some much less than the Mississippi.

Disintegrated matter is carried away by the wind as well as by 
running water.  During volcanic outbursts much rock is triturated 
and is thus widely dispersed; and in all arid countries the wind 
plays an important part in the removal of such matter.  Wind-driven 
sand also wears down the hardest rocks.  I have shown {60} that 
during four months of the year a large quantity of dust is blown 
from the north-western shores of Africa, and falls on the Atlantic 
over a space of 1600 miles in latitude, and for a distance of from 
300 to 600 miles from the coast.  But dust has been seen to fall at 
a distance of 1030 miles from the shores of Africa.  During a stay 
of three weeks at St. Jago in the Cape Verde Archipelago, the 
atmosphere was almost always hazy, and extremely fine dust coming 
from Africa was continually falling.  In some of this dust which 
fell in the open ocean at a distance of between 330 and 380 miles 
from the African coast, there were many particles of stone, about 
1/1000 of an inch square.  Nearer to the coast the water has been 
seen to be so much discoloured by the falling dust, that a sailing 
vessel left a track behind her.  In countries, like the Cape Verde 
Archipelago, where it seldom rains and there are no frosts, the 
solid rock nevertheless disintegrates; and in conformity with the 
views lately advanced by a distinguished Belgian geologist, De 
Koninck, such disintegration may be attributed in chief part to the 
action of the carbonic and nitric acids, together with the nitrates 
and nitrites of ammonia, dissolved in the dew.

In all humid, even moderately humid, countries, worms aid in the 
work of denudation in several ways.  The vegetable mould which 
covers, as with a mantle, the surface of the land, has all passed 
many times through their bodies.  Mould differs in appearance from 
the subsoil only in its dark colour, and in the absence of 
fragments or particles of stone (when such are present in the 
subsoil), larger than those which can pass through the alimentary 
canal of a worm.  This sifting of the soil is aided, as has already 
been remarked, by burrowing animals of many kinds, especially by 
ants.  In countries where the summer is long and dry, the mould in 
protected places must be largely increased by dust blown from other 
and more exposed places.  For instance, the quantity of dust 
sometimes blown over the plains of La Plata, where there are no 
solid rocks, is so great, that during the "gran seco," 1827 to 
1830, the appearance of the land, which is here unenclosed, was so 
completely changed that the inhabitants could not recognise the 
limits of their own estates, and endless lawsuits arose.  Immense 
quantities of dust are likewise blown about in Egypt and in the 
south of France.  In China, as Richthofen maintains, beds appearing 
like fine sediment, several hundred feet in thickness and extending 
over an enormous area, owe their origin to dust blown from the high 
lands of central Asia. {61}  In humid countries like Great Britain, 
as long as the land remains in its natural state clothed with 
vegetation, the mould in any one place can hardly be much increased 
by dust; but in its present condition, the fields near high roads, 
where there is much traffic, must receive a considerable amount of 
dust, and when fields are harrowed during dry and windy weather, 
clouds of dust may be seen to be blown away.  But in all these 
cases the surface-soil is merely transported from one place to 
another.  The dust which falls so thickly within our houses 
consists largely of organic matter, and if spread over the land 
would in time decay and disappear almost entirely.  It appears, 
however, from recent observations on the snow-fields of the Arctic 
regions, that some little meteoric dust of extra mundane origin is 
continually falling.

The dark colour of ordinary mould is obviously due to the presence 
of decaying organic matter, which, however, is present in but small 
quantities.  The loss of weight which mould suffers when heated to 
redness seems to be in large part due to water in combination being 
dispelled.  In one sample of fertile mould the amount of organic 
matter was ascertained to be only 1.76 per cent.; in some 
artificially prepared soil it was as much as 5.5 per cent., and in 
the famous black soil of Russia from 5 to even 12 per cent. {62}  
In leaf-mould formed exclusively by the decay of leaves the amount 
is much greater, and in peat the carbon alone sometimes amounts to 
64 per cent.; but with these latter cases we are not here 
concerned.  The carbon in the soil tends gradually to oxidise and 
to disappear, except where water accumulates and the climate is 
cool; {63} so that in the oldest pasture-land there is no great 
excess of organic matter, notwithstanding the continued decay of 
the roots and the underground stems of plants, and the occasional 
addition of manure.  The disappearance of the organic matter from 
mould is probably much aided by its being brought again and again 
to the surface in the castings of worms.

Worms, on the other hand, add largely to the organic matter in the 
soil by the astonishing number of half-decayed leaves which they 
draw into their burrows to a depth of 2 or 3 inches.  They do this 
chiefly for obtaining food, but partly for closing the mouths of 
their burrows and for lining the upper part.  The leaves which they 
consume are moistened, torn into small shreds, partially digested, 
and intimately commingled with earth; and it is this process which 
gives to vegetable mould its uniform dark tint.  It is known that 
various kinds of acids are generated by the decay of vegetable 
matter; and from the contents of the intestines of worms and from 
their castings being acid, it seems probable that the process of 
digestion induces an analogous chemical change in the swallowed, 
triturated, and half-decayed leaves.  The large quantity of 
carbonate of lime secreted by the calciferous glands apparently 
serves to neutralise the acids thus generated; for the digestive 
fluid of worms will not act unless it be alkaline.  As the contents 
of the upper part of their intestines are acid, the acidity can 
hardly be due to the presence of uric acid.  We may therefore 
conclude that the acids in the alimentary canal of worms are formed 
during the digestive process; and that probably they are nearly of 
the same nature as those in ordinary mould or humus.  The latter 
are well known to have the power of de-oxidising or dissolving per-
oxide of iron, as may be seen wherever peat overlies red sand, or 
where a rotten root penetrates such sand.  Now I kept some worms in 
a pot filled with very fine reddish sand, consisting of minute 
particles of silex coated with the red oxide of iron; and the 
burrows, which the worms made through this sand, were lined or 
coated in the usual manner with their castings, formed of the sand 
mingled with their intestinal secretions and the refuse of the 
digested leaves; and this sand had almost wholly lost its red 
colour.  When small portions of it were placed under the 
microscope, most of the grains were seen to be transparent and 
colourless, owing to the dissolution of the oxide; whilst almost 
all the grains taken from other parts of the pot were coated with 
the oxide.  Acetic acid produced hardly any effect on his sand; and 
even hydrochloric, nitric and sulphuric acids, diluted as in the 
Pharmacopoeia, produced less effect than did the acids in the 
intestines of the worms.

Mr. A. A. Julien has lately collected all the extant information 
about the acids generated in humus, which, according to some 
chemists, amount to more than a dozen different kinds.  These 
acids, as well as their acid salts (i.e., in combination with 
potash, soda, and ammonia), act energetically on carbonate of lime 
and on the oxides of iron.  It is also known that some of these 
acids, which were called long ago by Thenard azohumic, are enabled 
to dissolve colloid silica in proportion to the nitrogen which they 
contain. {64}  In the formation of these latter acids worms 
probably afford some aid, for Dr. H. Johnson informs me that by 
Nessler's test he found 0.018 per cent. of ammonia in their 
castings.

It may be here added that I have recently been informed by Dr. 
Gilbert "that several square yards on his lawn were swept clean, 
and after two or three weeks all the worm-castings on the space 
were collected and dried.  These were found to contain 0.35 of 
nitrogen.  This is from two to three times as much as we find in 
our ordinary arable surface-soil; more than in our ordinary pasture 
surface-soil; but less than in rich kitchen-garden mould.  
Supposing a quantity of castings equal to 10 tons in the dry state 
were annually deposited on an acre, this would represent a manuring 
of 78 lbs. of nitrogen per acre per annum; and this is very much 
more than the amount of nitrogen in the annual yield of hay per 
acre, if raised without any nitrogenous manure.  Obviously, so far 
as the nitrogen in the castings is derived from surface-growth or 
from surface-soil, it is not a gain to the latter; but so far as it 
is derived from below, it is a gain."

The several humus-acids, which appear, as we have just seen, to be 
generated within the bodies of worms during the digestive process, 
and their acid salts, play a highly important part, according to 
the recent observations of Mr. Julien, in the disintegration of 
various kinds of rocks.  It has long been known that the carbonic 
acid, and no doubt nitric and nitrous acids, which are present in 
rain-water, act in like manner.  There is, also, a great excess of 
carbonic acid in all soils, especially in rich soils, and this is 
dissolved by the water in the ground.  The living roots of plants, 
moreover, as Sachs and others have shown, quickly corrode and leave 
their impressions on polished slabs of marble, dolomite and 
phosphate of lime.  They will attack even basalt and sandstone. 
{65}  But we are not here concerned with agencies which are wholly 
independent of the action of worms.

The combination of any acid with a base is much facilitated by 
agitation, as fresh surfaces are thus continually brought into 
contact.  This will be thoroughly effected with the particles of 
stone and earth in the intestines of worms, during the digestive 
process; and it should be remembered that the entire mass of the 
mould over every field, passes, in the course of a few years, 
through their alimentary canals.  Moreover as the old burrows 
slowly collapse, and as fresh castings are continually brought to 
the surface, the whole superficial layer of mould slowly revolves 
or circulates; and the friction of the particles one with another 
will rub off the finest films of disintegrated matter as soon as 
they are formed.  Through these several means, minute fragments of 
rocks of many kinds and mere particles in the soil will be 
continually exposed to chemical decomposition; and thus the amount 
of soil will tend to increase.

As worms line their burrows with their castings, and as the burrows 
penetrate to a depth of 5 or 6, or even more feet, some small 
amount of the humus-acids will be carried far down, and will there 
act on the underlying rocks and fragments of rock.  Thus the 
thickness of the soil, if none be removed from the surface, will 
steadily though slowly tend to increase; but the accumulation will 
after a time delay the disintegration of the underlying rocks and 
of the more deeply seated particles.  For the humus-acids which are 
generated chiefly in the upper layer of vegetable mould, are 
extremely unstable compounds, and are liable to decomposition 
before they reach any considerable depth. {66}  A thick bed of 
overlying soil will also check the downward extension of great 
fluctuations of temperature, and in cold countries will check the 
powerful action of frost.  The free access of air will likewise be 
excluded.  From these several causes disintegration would be almost 
arrested, if the overlying mould were to increase much in 
thickness, owing to none or little being removed from the surface. 
{67}  In my own immediate neighbourhood we have a curious proof how 
effectually a few feet of clay checks some change which goes on in 
flints, lying freely exposed; for the large ones which have lain 
for some time on the surface of ploughed fields cannot be used for 
building; they will not cleave properly, and are said by the 
workmen to be rotten. {68}  It is therefore necessary to obtain 
flints for building purposes from the bed of red clay overlying the 
chalk (the residue of its dissolution by rain-water) or from the 
chalk itself.

Not only do worms aid directly in the chemical disintegration of 
rocks, but there is good reason to believe that they likewise act 
in a direct and mechanical manner on the smaller particles.  All 
the species which swallow earth are furnished with gizzards; and 
these are lined with so thick a chitinous membrane, that Perrier 
speaks of it, {69} as "une veritable armature."  The gizzard is 
surrounded by powerful transverse muscles, which, according to 
Claparede, are about ten times as thick as the longitudinal ones; 
and Perrier saw them contracting energetically.  Worms belonging to 
one genus, Digaster, have two distinct but quite similar gizzards; 
and in another genus, Moniligaster, the second gizzard consists of 
four pouches, one succeeding the other, so that it may almost be 
said to have five gizzards. {70}  In the same manner as 
gallinaceous and struthious birds swallow stones to aid in the 
trituration of their food, so it appears to be with terricolous 
worms.  The gizzards of thirty-eight of our common worms were 
opened, and in twenty-five of them small stones or grains of sand, 
sometimes together with the hard calcareous concretions formed 
within the anterior calciferous glands, were found, and in two 
others concretions alone.  In the gizzards of the remaining worms 
there were no stones; but some of these were not real exceptions, 
as the gizzards were opened late in the autumn, when the worms had 
ceased to feed and their gizzards were quite empty. {71}

When worms make their burrows through earth abounding with little 
stones, no doubt many will be unavoidably swallowed; but it must 
not be supposed that this fact accounts for the frequency with 
which stones and sand are found in their gizzards.  For beads of 
glass and fragments of brick and of hard tiles were scattered over 
the surface of the earth, in pots in which worms were kept and had 
already made their burrows; and very many of these beads and 
fragments were picked up and swallowed by the worms, for they were 
found in their castings, intestines, and gizzards.  They even 
swallowed the coarse red dust, formed by the pounding of the tiles.  
Nor can it be supposed that they mistook the beads and fragments 
for food; for we have seen that their taste is delicate enough to 
distinguish between different kinds of leaves.  It is therefore 
manifest that they swallow hard objects, such as bits of stone, 
beads of glass and angular fragments of bricks or tiles for some 
special purpose; and it can hardly be doubted that this is to aid 
their gizzards in crushing and grinding the earth, which they so 
largely consume.  That such hard objects are not necessary for 
crushing leaves, may be inferred from the fact that certain 
species, which live in mud or water and feed on dead or living 
vegetable matter, but which do not swallow earth, are not provided 
with gizzards, {72} and therefore cannot have the power of 
utilising stones.

During the grinding process, the particles of earth must be rubbed 
against one another, and between the stones and the tough lining 
membrane of the gizzard.  The softer particles will thus suffer 
some attrition, and will perhaps even be crushed.  This conclusion 
is supported by the appearance of freshly ejected castings, for 
these often reminded me of the appearance of paint which has just 
been ground by a workman between two flat stones.  Morren remarks 
that the intestinal canal is "impleta tenuissima terra, veluti in 
pulverem redacta." {73}  Perrier also speaks of "l'etat de pate 
excessivement fine a laquelle est reduite la terre qu'ils 
rejettent," &c. {74}

As the amount of trituration which the particles of earth undergo 
in the gizzards of worms possesses some interest (as we shall 
hereafter see), I endeavoured to obtain evidence on this head by 
carefully examining many of the fragments which had passed through 
their alimentary canals.  With worms living in a state of nature, 
it is of course impossible to know how much the fragments may have 
been worn before they were swallowed.  It is, however, clear that 
worms do not habitually select already rounded particles, for 
sharply angular bits of flint and of other hard rocks were often 
found in their gizzards or intestines.  On three occasions sharp 
spines from the stems of rose-bushes were thus found.  Worms kept 
in confinement repeatedly swallowed angular fragments of hard tile, 
coal, cinders, and even the sharpest fragments of glass.  
Gallinaceous and struthious birds retain the same stones in their 
gizzards for a long time, which thus become well rounded; but this 
does not appear to be the case with worms, judging from the large 
number of the fragments of tiles, glass beads, stones, &c., 
commonly found in their castings and intestines.  So that unless 
the same fragments were to pass repeatedly through their gizzards, 
visible signs of attrition in the fragments could hardly be 
expected, except perhaps in the case of very soft stones.

I will now give such evidence of attrition as I have been able to 
collect.  In the gizzards of some worms dug out of a thin bed of 
mould over the chalk, there were many well-rounded small fragments 
of chalk, and two fragments of the shells of a land-mollusc (as 
ascertained by their microscopical structure), which latter were 
not only rounded but somewhat polished.  The calcareous concretions 
formed in the calciferous glands, which are often found in their 
gizzards, intestines, and occasionally in their castings, when of 
large size, sometimes appeared to have been rounded; but with all 
calcareous bodies the rounded appearance may be partly or wholly 
due to their corrosion by carbonic acid and the humus-acids.  In 
the gizzards of several worms collected in my kitchen garden near a 
hothouse, eight little fragments of cinders were found, and of 
these, six appeared more or less rounded, as were two bits of 
brick; but some other bits were not at all rounded.  A farm-road 
near Abinger Hall had been covered seven years before with brick-
rubbish to the depth of about 6 inches; turf had grown over this 
rubbish on both sides of the road for a width of 18 inches, and on 
this turf there were innumerable castings.  Some of them were 
coloured of a uniform red owing to the presence of much brick-dust, 
and they contained many particles of brick and of hard mortar from 
1 to 3 mm. in diameter, most of which were plainly rounded; but all 
these particles may have been rounded before they were protected by 
the turf and were swallowed, like those on the bare parts of the 
road which were much worn.  A hole in a pasture-field had been 
filled up with brick-rubbish at the same time, viz., seven years 
ago, and was now covered with turf; and here the castings contained 
very many particles of brick, all more or less rounded; and this 
brick-rubbish, after being shot into the hole, could not have 
undergone any attrition.  Again, old bricks very little broken, 
together with fragments of mortar, were laid down to form walks, 
and were then covered with from 4 to 6 inches of gravel; six little 
fragments of brick were extracted from castings collected on these 
walks, three of which were plainly worn.  There were also very many 
particles of hard mortar, about half of which were well rounded; 
and it is not credible that these could have suffered so much 
corrosion from the action of carbonic acid in the course of only 
seven years.

Much better evidence of the attrition of hard objects in the 
gizzards of worms, is afforded by the state of the small fragments 
of tiles or bricks, and of concrete in the castings thrown up where 
ancient buildings once stood.  As all the mould covering a field 
passes every few years through the bodies of worms, the same small 
fragments will probably be swallowed and brought to the surface 
many times in the course of centuries.  It should be premised that 
in the several following cases, the finer matter was first washed 
away from the castings, and then all the particles of bricks, tiles 
and concrete were collected without any selection, and were 
afterwards examined.  Now in the castings ejected between the 
tesserae on one of the buried floors of the Roman villa at Abinger, 
there were many particles (from to 2 mm. in diameter) of tiles and 
concrete, which it was impossible to look at with the naked eye or 
through a strong lens, and doubt for a moment that they had almost 
all undergone much attrition.  I speak thus after having examined 
small water-worn pebbles, formed from Roman bricks, which M. Henri 
de Saussure had the kindness to send me, and which he had extracted 
from sand and gravel beds, deposited on the shores of the Lake of 
Geneva, at a former period when the water stood at about two metres 
above its present level.  The smallest of these water-worn pebbles 
of brick from Geneva resembled closely many of those extracted from 
the gizzards of worms, but the larger ones were somewhat smoother.

Four castings found on the recently uncovered, tesselated floor of 
the great room in the Roman villa at Brading, contained many 
particles of tile or brick, of mortar, and of hard white cement; 
and the majority of these appeared plainly worn.  The particles of 
mortar, however, seemed to have suffered more corrosion than 
attrition, for grains of silex often projected from their surfaces.  
Castings from within the nave of Beaulieu Abbey, which was 
destroyed by Henry VIII., were collected from a level expanse of 
turf, overlying the buried tesselated pavement, through which worm-
burrows passed; and these castings contained innumerable particles 
of tiles and bricks, of concrete and cement, the majority of which 
had manifestly undergone some or much attrition.  There were also 
many minute flakes of a micaceous slate, the points of which were 
rounded.  If the above supposition, that in all these cases the 
same minute fragments have passed several times through the 
gizzards of worms, be rejected, notwithstanding its inherent 
probability, we must then assume that in all the above cases the 
many rounded fragments found in the castings had all accidentally 
undergone much attrition before they were swallowed; and this is 
highly improbable.

On the other hand it must be stated that fragments of ornamental 
tiles, somewhat harder than common tiles or bricks, which had been 
swallowed only once by worms kept in confinement, were with the 
doubtful exception of one or two of the smallest grains, not at all 
rounded.  Nevertheless some of them appeared a little worn, though 
not rounded.  Notwithstanding these cases, if we consider the 
evidence above given, there can be little doubt that the fragments, 
which serve as millstones in the gizzards of worms, suffer, when of 
a not very hard texture, some amount of attrition; and that the 
smaller particles in the earth, which is habitually swallowed in 
such astonishingly large quantities by worms, are ground together 
and are thus levigated.  If this be the case, the "terra 
tenuissima,"--the "pate excessivement fine,"--of which the castings 
largely consist, is in part due to the mechanical action of the 
gizzard; {75} and this fine matter, as we shall see in the next 
chapter, is that which is chiefly washed away from the innumerable 
castings on every field during each heavy shower of rain.  If the 
softer stones yield at all, the harder ones will suffer some slight 
amount of wear and tear.

The trituration of small particles of stone in the gizzards of 
worms is of more importance under a geological point of view than 
may at first appear to be the case; for Mr. Sorby has clearly shown 
that the ordinary means of disintegration, namely, running water 
and the waves of the sea, act with less and less power on fragments 
of rock the smaller they are.  "Hence," as he remarks, "even making 
no allowance for the extra buoying up of very minute particles by a 
current of water, depending on surface cohesion, the effects of 
wearing on the form of the grains must vary directly as their 
diameter or thereabouts.  If so, a grain of 1/10 an inch in 
diameter would be worn ten times as much as one of an inch in 
diameter, and at least a hundred times as much as one of 1/100 an 
inch in diameter.  Perhaps, then, we may conclude that a grain 1/10 
of an inch in diameter would be worn as much or more in drifting a 
mile as a grain 1/1000 of an inch in being drifted 100 miles.  On 
the same principle a pebble one inch in diameter would be worn 
relatively more by being drifted only a few hundred yards." {76}  
Nor should we forget, in considering the power which worms exert in 
triturating particles of rock, that there is good evidence that on 
each acre of land, which is sufficiently damp and not too sandy, 
gravelly or rocky for worms to inhabit, a weight of more than ten 
tons of earth annually passes through their bodies and is brought 
to the surface.  The result for a country of the size of Great 
Britain, within a period not very long in a geological sense, such 
as a million years, cannot be insignificant; for the ten tons of 
earth has to be multiplied first by the above number of years, and 
then by the number of acres fully stocked with worms; and in 
England, together with Scotland, the land which is cultivated and 
is well fitted for these animals, has been estimated at above 32 
million acres.  The product is 320 million million tons of earth.



CHAPTER VI--THE DENUDATION OF THE LAND--continued.



Denudation aided by recently ejected castings flowing down inclined 
grass-covered surfaces--The amount of earth which annually flows 
downwards--The effect of tropical rain on worm castings--The finest 
particles of earth washed completely away from castings--The 
disintegration of dried castings into pellets, and their rolling 
down inclined surfaces--The formation of little ledges on hill-
sides, in part due to the accumulation of disintegrated castings--
Castings blown to leeward over level land--An attempt to estimate 
the amount thus blown--The degradation of ancient encampments and 
tumuli--The preservation of the crowns and furrows on land 
anciently ploughed--The formation and amount of mould over the 
Chalk formation.

We are now prepared to consider the more direct part which worms 
take in the denudation of the land.  When reflecting on sub-aerial 
denudation, it formerly appeared to me, as it has to others, that a 
nearly level or very gently inclined surface, covered with turf, 
could suffer no loss during even a long lapse of time.  It may, 
however, be urged that at long intervals, debacles of rain or 
water-spouts would remove all the mould from a very gentle slope; 
but when examining the steep, turf-covered slopes in Glen Roy, I 
was struck with the fact how rarely any such event could have 
happened since the Glacial period, as was plain from the well-
preserved state of the three successive "roads" or lake-margins.  
But the difficulty in believing that earth in any appreciable 
quantity can be removed from a gently inclined surface, covered 
with vegetation and matted with roots, is removed through the 
agency of worms.  For the many castings which are thrown up during 
rain, and those thrown up some little time before heavy rain, flow 
for a short distance down an inclined surface.  Moreover much of 
the finest levigated earth is washed completely away from the 
castings.  During dry weather castings often disintegrate into 
small rounded pellets, and these from their weight often roll down 
any slope.  This is more especially apt to occur when they are 
started by the wind, and probably when started by the touch of an 
animal, however small.  We shall also see that a strong wind blows 
all the castings, even on a level field, to leeward, whilst they 
are soft; and in like manner the pellets when they are dry.  If the 
wind blows in nearly the direction of an inclined surface, the 
flowing down of the castings is much aided.

The observations on which these several statements are founded must 
now be given in some detail.  Castings when first ejected are 
viscid and soft; during rain, at which time worms apparently prefer 
to eject them, they are still softer; so that I have sometimes 
thought that worms must swallow much water at such times.  However 
this may be, rain, even when not very heavy, if long continued, 
renders recently-ejected castings semi-fluid; and on level ground 
they then spread out into thin, circular, flat discs, exactly as 
would so much honey or very soft mortar, with all traces of their 
vermiform structure lost.  This latter fact was sometimes made 
evident, when a worm had subsequently bored through a flat circular 
disc of this kind, and heaped up a fresh vermiform mass in the 
centre.  These flat subsided discs have been repeatedly seen by me 
after heavy rain, in many places on land of all kinds.

On the flowing of wet castings, and the rolling of dry 
disintegrated castings down inclined surfaces.--When castings are 
ejected on an inclined surface during or shortly before heavy rain, 
they cannot fail to flow a little down the slope.  Thus, on some 
steep slopes in Knole Park, which were covered with coarse grass 
and had apparently existed in this state from time immemorial, I 
found (Oct. 22, 1872) after several wet days that almost all the 
many castings were considerably elongated in the line of the slope; 
and that they now consisted of smooth, only slightly conical 
masses.  Whenever the mouths of the burrows could be found from 
which the earth had been ejected, there was more earth below than 
above them.  After some heavy storms of rain (Jan. 25, 1872) two 
rather steeply inclined fields near Down, which had formerly been 
ploughed and were now rather sparsely clothed with poor grass, were 
visited, and many castings extended down the slopes for a length of 
5 inches, which was twice or thrice the usual diameter of the 
castings thrown up on the level parts of these same fields.  On 
some fine grassy slopes in Holwood Park, inclined at angles between 
8 degrees and 11 degrees 30 seconds with the horizon, where the 
surface apparently had never been disturbed by the hand of man, 
castings abounded in extraordinary numbers:  and a space 16 inches 
in length transversely to the slope and 6 inches in the line of the 
slope, was completely coated, between the blades of grass, with a 
uniform sheet of confluent and subsided castings.  Here also in 
many places the castings had flowed down the slope, and now formed 
smooth narrow patches of earth, 6, 7, and 7.5 inches in length.  
Some of these consisted of two castings, one above the other, which 
had become so completely confluent that they could hardly be 
distinguished.  On my lawn, clothed with very fine grass, most of 
the castings are black, but some are yellowish from earth having 
been brought up from a greater depth than usual, and the flowing-
down of these yellow castings after heavy rain, could be clearly 
seen where the slope was 5 degrees; and where it was less than 1 
degree some evidence of their flowing down could still be detected.  
On another occasion, after rain which was never heavy, but which 
lasted for 18 hours, all the castings on this same gently inclined 
lawn had lost their vermiform structure; and they had flowed, so 
that fully two-thirds of the ejected earth lay below the mouths of 
the burrows.

These observations led me to make others with more care.  Eight 
castings were found on my lawn, where the grass-blades are fine and 
close together, and three others on a field with coarse grass.  The 
inclination of the surface at the eleven places where these 
castings were collected varied between 4 degrees 30 seconds and 17 
degrees 30 seconds; the mean of the eleven inclinations being 9 
degrees 26 seconds.  The length of the castings in the direction of 
the slope was first measured with as much accuracy as their 
irregularities would permit.  It was found possible to make these 
measurements within about of an inch, but one of the castings was 
too irregular to admit of measurement.  The average length in the 
direction of the slope of the remaining ten castings was 2.03 
inches.  The castings were then divided with a knife into two parts 
along a horizontal line passing through the mouth of the burrow, 
which was discovered by slicing off the turf; and all the ejected 
earth was separately collected, namely, the part above the hole and 
the part below.  Afterwards these two parts were weighed.  In every 
case there was much more earth below than above; the mean weight of 
that above being 103 grains, and of that below 205 grains; so that 
the latter was very nearly double the former.  As on level ground 
castings are commonly thrown up almost equally round the mouths of 
the burrows, this difference in weight indicates the amount of 
ejected earth which had flowed down the slope.  But very many more 
observations would be requisite to arrive at any general result; 
for the nature of the vegetation and other accidental 
circumstances, such as the heaviness of the rain, the direction and 
force of the wind, &c., appear to be more important in determining 
the quantity of the earth which flows down a slope than its angle.  
Thus with four castings on my lawn (included in the above eleven) 
where the mean slope was 7 degrees 19 seconds, the difference in 
the amount of earth above and below the burrows was greater than 
with three other castings on the same lawn where the mean slope was 
12 degrees 5 seconds.

We may, however, take the above eleven cases, which are accurate as 
far as they go, and calculate the weight of the ejected earth which 
annually flows down a slope having a mean inclination of 9 degrees 
26 seconds.  This was done by my son George.  It has been shown 
that almost exactly two-thirds of the ejected earth is found below 
the mouth of the burrow and one-third above it.  Now if the two-
thirds which is below the hole be divided into two equal parts, the 
upper half of this two-thirds exactly counterbalances the one-third 
which is above the hole, so that as far as regards the one-third 
above and the upper half of the two-thirds below, there is no flow 
of earth down the hill-side.  The earth constituting the lower half 
of the two-thirds is, however, displaced through distances which 
are different for every part of it, but which may be represented by 
the distance between the middle point of the lower half of the two-
thirds and the hole.  So that the average distance of displacement 
is a half of the whole length of the worm-casting.  Now the average 
length of ten out of the above eleven castings was 2.03 inches, and 
half of this we may take as being 1 inch.  It may therefore be 
concluded that one-third of the whole earth brought to the surface 
was in these cases carried down the slope through 1 inch. {77}

It was shown in the third chapter that on Leith Hill Common, dry 
earth weighing at least 7.453 lbs. was brought up by worms to the 
surface on a square yard in the course of a year.  If a square yard 
be drawn on a hillside with two of its sides horizontal, then it is 
clear that only 1/36 part of the earth brought up on that square 
yard would be near enough to its lower side to cross it, supposing 
the displacement of the earth to be through one inch.  But it 
appears that only of the earth brought up can be considered to flow 
downwards; hence 1/3 of 1/36 or 1/108 of 7.453 lbs. will cross the 
lower side of our square yard in a year.  Now 1/108 of 7.453 lbs. 
is 1.1 oz.  Therefore 1.1 oz. of dry earth will annually cross each 
linear yard running horizontally along a slope having the above 
inclination; or very nearly 7 lbs. will annually cross a horizontal 
line, 100 yards in length, on a hill-side having this inclination.

A more accurate, though still very rough, calculation can be made 
of the bulk of earth, which in its natural damp state annually 
flows down the same slope over a yard-line drawn horizontally 
across it.  From the several cases given in the third chapter, it 
is known that the castings annually brought to the surface on a 
square yard, if uniformly spread out would form a layer 0.2 of an 
inch in thickness:  it therefore follows by a calculation similar 
to the one already given, that 1/3 of 0.2x36, or 2.4 cubic inches 
of damp earth will annually cross a horizontal line one yard in 
length on a hillside with the above inclination.  This bulk of damp 
castings was found to weigh 1.85 oz.  Therefore 11.56 lbs. of damp 
earth, instead of 7 lbs. of dry earth as by the former calculation, 
would annually cross a line 100 yards in length on our inclined 
surface.

In these calculations it has been assumed that the castings flow a 
short distance downwards during the whole year, but this occurs 
only with those ejected during or shortly before rain; so that the 
above results are thus far exaggerated.  On the other hand, during 
rain much of the finest earth is washed to a considerable distance 
from the castings, even where the slope is an extremely gentle one, 
and is thus wholly lost as far as the above calculations are 
concerned.  Castings ejected during dry weather and which have set 
hard, lose in the same manner a considerable quantity of fine 
earth.  Dried castings, moreover, are apt to disintegrate into 
little pellets, which often roll or are blown down any inclined 
surface.  Therefore the above result, namely, that 24 cubic inches 
of earth (weighing 1.85 oz. whilst damp) annually crosses a yard-
line of the specified kind, is probably not much if at all 
exaggerated.

This amount is small; but we should bear in mind how many branching 
valleys intersect most countries, the whole length of which must be 
very great; and that earth is steadily travelling down both turf-
covered sides of each valley.  For every 100 yards in length in a 
valley with sides sloping as in the foregoing cases, 480 cubic 
inches of damp earth, weighing above 23 pounds, will annually reach 
the bottom.  Here a thick bed of alluvium will accumulate, ready to 
be washed away in the course of centuries, as the stream in the 
middle meanders from side to side.

If it could be shown that worms generally excavate their burrows at 
right angles to an inclined surface, and this would be their 
shortest course for bringing up earth from beneath, then as the old 
burrows collapsed from the weight of the superincumbent soil, the 
collapsing would inevitably cause the whole bed of vegetable mould 
to sink or slide slowly down the inclined surface.  But to 
ascertain the direction of many burrows was found too difficult and 
troublesome.  A straight piece of wire was, however, pushed into 
twenty-five burrows on several sloping fields, and in eight cases 
the burrows were nearly at right angles to the slope; whilst in the 
remaining cases they were indifferently directed at various angles, 
either upwards or downwards with respect to the slope.

In countries where the rain is very heavy, as in the tropics, the 
castings appear, as might have been expected, to be washed down in 
a greater degree than in England.  Mr. Scott informs me that near 
Calcutta the tall columnar castings (previously described), the 
diameter of which is usually between 1 and 1.5 inch, subside on a 
level surface, after heavy rain, into almost circular, thin, flat 
discs, between 3 and 4 and sometimes 5 inches in diameter.  Three 
fresh castings, which had been ejected in the Botanic Gardens "on a 
slightly inclined, grass-covered, artificial bank of loamy clay," 
were carefully measured, and had a mean height of 2.17, and a mean 
diameter of 1.43 inches; these after heavy rain, formed elongated 
patches of earth, with a mean length in the direction of the slope 
of 5.83 inches.  As the earth had spread very little up the slope, 
a large part, judging from the original diameter of these castings, 
must have flowed bodily downwards about 4 inches.  Moreover some of 
the finest earth of which they were composed must have been washed 
completely away to a still greater distance.  In drier sites near 
Calcutta, a species of worm ejects its castings, not in vermiform 
masses, but in little pellets of varying sizes:  these are very 
numerous in some places, and Mr. Scott says that they "are washed 
away by every shower."

I was led to believe that a considerable quantity of fine earth is 
washed quite away from castings during rain, from the surfaces of 
old ones being often studded with coarse particles.  Accordingly a 
little fine precipitated chalk, moistened with saliva or gum-water, 
so as to be slightly viscid and of the same consistence as a fresh 
casting, was placed on the summits of several castings and gently 
mixed with them.  These castings were then watered through a very 
fine rose, the drops from which were closer together than those of 
rain, but not nearly so large as those in a thunderstorm; nor did 
they strike the ground with nearly so much force as drops during 
heavy rain.  A casting thus treated subsided with surprising 
slowness, owing as I suppose to its viscidity.  It did not flow 
bodily down the grass-covered surface of the lawn, which was here 
inclined at an angle of 16 degrees 20 seconds; nevertheless many 
particles of the chalk were found three inches below the casting.  
The experiment was repeated on three other castings on different 
parts of the lawn, which sloped at 2 degrees 30 seconds, 3 degrees 
and 6 degrees; and particles of chalk could be seen between 4 and 5 
inches below the casting; and after the surface had become dry, 
particles were found in two cases at a distance of 5 and 6 inches.  
Several other castings with precipitated chalk placed on their 
summits were left to the natural action of the rain.  In one case, 
after rain which was not heavy, the casting was longitudinally 
streaked with white.  In two other cases the surface of the ground 
was rendered somewhat white for a distance of one inch from the 
casting; and some soil collected at a distance of 2.5 inches, where 
the slope was 7 degrees, effervesced slightly when placed in acid.  
After one or two weeks, the chalk was wholly or almost wholly 
washed away from all the castings on which it had been placed, and 
these had recovered their natural colour.

It may be here remarked that after very heavy rain shallow pools 
may be seen on level or nearly level fields, where the soil is not 
very porous, and the water in them is often slightly muddy; when 
such little pools have dried, the leaves and blades of grass at 
their bottoms are generally coated with a thin layer of mud.  This 
mud I believe is derived in large part from recently ejected 
castings.

Dr. King informs me that the majority of the before described 
gigantic castings, which he found on a fully exposed, bare, 
gravelly knoll on the Nilgiri Mountains in India, had been more or 
less weathered by the previous north-east monsoon; and most of them 
presented a subsided appearance.  The worms here eject their 
castings only during the rainy season; and at the time of Dr. 
King's visit no rain had fallen for 110 days.  He carefully 
examined the ground between the place where these huge castings 
lay, and a little watercourse at the base of the knoll, and nowhere 
was there any accumulation of fine earth, such as would necessarily 
have been left by the disintegration of the castings if they had 
not been wholly removed.  He therefore has no hesitation in 
asserting that the whole of these huge castings are annually washed 
during the two monsoons (when about 100 inches of rain fall) into 
the little water-course, and thence into the plains lying below at 
a depth of 3000 or 4000 feet.

Castings ejected before or during dry weather become hard, 
sometimes surprisingly hard, from the particles of earth having 
been cemented together by the intestinal secretions.  Frost seems 
to be less effective in their disintegration than might have been 
expected.  Nevertheless they readily disintegrate into small 
pellets, after being alternately moistened with rain and again 
dried.  Those which have flowed during rain down a slope, 
disintegrate in the same manner.  Such pellets often roll a little 
down any sloping surface; their descent being sometimes much aided 
by the wind.  The whole bottom of a broad dry ditch in my grounds, 
where there were very few fresh castings, was completely covered 
with these pellets or disintegrated castings, which had rolled down 
the steep sides, inclined at an angle of 27 degrees.

Near Nice, in places where the great cylindrical castings, 
previously described, abound, the soil consists of very fine 
arenaceo-calcareous loam; and Dr. King informs me that these 
castings are extremely liable to crumble during dry weather into 
small fragments, which are soon acted on by rain, and then sink 
down so as to be no longer distinguishable from the surrounding 
soil.  He sent me a mass of such disintegrated castings, collected 
on the top of a bank, where none could have rolled down from above.  
They must have been ejected within the previous five or six months, 
but they now consisted of more or less rounded fragments of all 
sizes, from 0.75 of an inch in diameter to minute grains and mere 
dust.  Dr. King witnessed the crumbling process whilst drying some 
perfect castings, which he afterwards sent me.  Mr. Scott also 
remarks on the crumbling of the castings near Calcutta and on the 
mountains of Sikkim during the hot and dry season.

When the castings near Nice had been ejected on an inclined 
surface, the disintegrated fragments rolled downwards, without 
losing their distinctive shape; and in some places could "be 
collected in basketfuls."  Dr. King observed a striking instance of 
this fact on the Corniche road, where a drain, about 2.5 feet wide 
and 9 inches deep, had been made to catch the surface drainage from 
the adjoining hill-side.  The bottom of this drain was covered for 
a distance of several hundred yards, to a depth of from 1.5 to 3 
inches, by a layer of broken castings, still retaining their 
characteristic shape.  Nearly all these innumerable fragments had 
rolled down from above, for extremely few castings had been ejected 
in the drain itself.  The hill-side was steep, but varied much in 
inclination, which Dr. King estimated at from 30 degrees to 60 
degrees with the horizon.  He climbed up the slope, and "found 
every here and there little embankments, formed by fragments of the 
castings that had been arrested in their downward progress by 
irregularities of the surface, by stones, twigs, &c.  One little 
group of plants of Anemone hortensis had acted in this manner, and 
quite a small bank of soil had collected round it.  Much of this 
soil had crumbled down, but a great deal of it still retained the 
form of castings."  Dr. King dug up this plant, and was struck with 
the thickness of the soil which must have recently accumulated over 
the crown of the rhizoma, as shown by the length of the bleached 
petioles, in comparison with those of other plants of the same 
kind, where there had been no such accumulation.  The earth thus 
accumulated had no doubt been secured (as I have everywhere seen) 
by the smaller roots of the plants.  After describing this and 
other analogous cases, Dr. King concludes:  "I can have no doubt 
that worms help greatly in the process of denudation."

Ledges of earth on steep hill-sides.--Little horizontal ledges, one 
above another, have been observed on steep grassy slopes in many 
parts of the world.  The formation has been attributed to animals 
travelling repeatedly along the slope in the same horizontal lines 
while grazing, and that they do thus move and use the ledges is 
certain; but Professor Henslow (a most careful observer) told Sir 
J. Hooker that he was convinced that this was not the sole cause of 
their formation.  Sir J. Hooker saw such ledges on the Himalayan 
and Atlas ranges, where there were no domesticated animals and not 
many wild ones; but these latter would, it is probable, use the 
ledges at night while grazing like our domesticated animals.  A 
friend observed for me the ledges on the Alps of Switzerland, and 
states that they ran at 3 or 4 ft. one above the other, and were 
about a foot in breadth.  They had been deeply pitted by the feet 
of grazing cows.  Similar ledges were observed by the same friend 
on our Chalk downs, and on an old talus of chalk-fragments (thrown 
out of a quarry) which had become clothed with turf.

My son Francis examined a Chalk escarpment near Lewes; and here on 
a part which was very steep, sloping at 40 degrees with the 
horizon, about 30 flat ledges extended horizontally for more than 
100 yards, at an average distance of about 20 inches, one beneath 
the other.  They were from 9 to 10 inches in breadth.  When viewed 
from a distance they presented a striking appearance, owing to 
their parallelism; but when examined closely, they were seen to be 
somewhat sinuous, and one often ran into another, giving the 
appearance of the ledge having forked into two.  They are formed of 
light-coloured earth, which on the outside, where thickest, was in 
one case 9 inches, and in another case between 6 and 7 inches in 
thickness.  Above the ledges, the thickness of the earth over the 
chalk was in the former case 4 and in the latter only 3 inches.  
The grass grew more vigorously on the outer edges of the ledges 
than on any other part of the slope, and here formed a tufted 
fringe.  Their middle part was bare, but whether this had been 
caused by the trampling of sheep, which sometimes frequent the 
ledges, my son could not ascertain.  Nor could he feel sure how 
much of the earth on the middle and bare parts, consisted of 
disintegrated worm-castings which had rolled down from above; but 
he felt convinced that some had thus originated; and it was 
manifest that the ledges with their grass-fringed edges would 
arrest any small object rolling down from above.

At one end or side of the bank bearing these ledges, the surface 
consisted in parts of bare chalk, and here the ledges were very 
irregular.  At the other end of the bank, the slope suddenly became 
less steep, and here the ledges ceased rather abruptly; but little 
embankments only a foot or two in length were still present.  The 
slope became steeper lower down the hill, and the regular ledges 
then reappeared.  Another of my sons observed, on the inland side 
of Beachy Head, where the surface sloped at about 25 degrees, many 
short little embankments like those just mentioned.  They extended 
horizontally and were from a few inches to two or three feet in 
length.  They supported tufts of grass growing vigorously.  The 
average thickness of the mould of which they were formed, taken 
from nine measurements, was 4.5 inches; while that of the mould 
above and beneath them was on an average only 3.2 inches, and on 
each side, on the same level, 3.1 inches.  On the upper parts of 
the slope, these embankments showed no signs of having been 
trampled on by sheep, but in the lower parts such signs were fairly 
plain.  No long continuous ledges had here been formed.

If the little embankments above the Corniche road, which Dr. King 
saw in the act of formation by the accumulation of disintegrated 
and rolled worm-castings, were to become confluent along horizontal 
lines, ledges would be formed.  Each embankment would tend to 
extend laterally by the lateral extension of the arrested castings; 
and animals grazing on a steep slope would almost certainly make 
use of every prominence at nearly the same level, and would indent 
the turf between them; and such intermediate indentations would 
again arrest the castings.  An irregular ledge when once formed 
would also tend to become more regular and horizontal by some of 
the castings rolling laterally from the higher to the lower parts, 
which would thus be raised.  Any projection beneath a ledge would 
not afterwards receive disintegrated matter from above, and would 
tend to be obliterated by rain and other atmospheric agencies.  
There is some analogy between the formation, as here supposed, of 
these ledges, and that of the ripples of wind-drifted sand as 
described by Lyell. {78}

The steep, grass-covered sides of a mountainous valley in 
Westmoreland, called Grisedale, was marked in many places with 
innumerable lines of miniature cliffs, with almost horizontal, 
little ledges at their bases.  Their formation was in no way 
connected with the action of worms, for castings could not anywhere 
be seen (and their absence is an inexplicable fact), although the 
turf lay in many places over a considerable thickness of boulder-
clay and moraine rubbish.  Nor, as far as I could judge, was the 
formation of these little cliffs at all closely connected with the 
trampling of cows or sheep.  It appeared as if the whole 
superficial, somewhat argillaceous earth, while partially held 
together by the roots of the grasses, had slided a little way down 
the mountain sides; and in thus sliding, had yielded and cracked in 
horizontal lines, transversely to the slope.

Castings blown to leeward by the wind.--We have seen that moist 
castings flow, and that disintegrated castings roll down any 
inclined surface; and we shall now see that castings, recently 
ejected on level grass-covered surfaces, are blown during gales of 
wind accompanied by rain to leeward.  This has been observed by me 
many times on many fields during several successive years.  After 
such gales, the castings present a gently inclined and smooth, or 
sometimes furrowed, surface to windward, while they are steeply 
inclined or precipitous to leeward, so that they resemble on a 
miniature scale glacier-ground hillocks of rock.  They are often 
cavernous on the leeward side, from the upper part having curled 
over the lower part.  During one unusually heavy south-west gale 
with torrents of rain, many castings were wholly blown to leeward, 
so that the mouths of the burrows were left naked and exposed on 
the windward side.  Recent castings naturally flow down an inclined 
surface, but on a grassy field, which sloped between 10 degrees and 
15 degrees, several were found after a heavy gale blown up the 
slope.  This likewise occurred on another occasion on a part of my 
lawn where the slope was somewhat less.  On a third occasion, the 
castings on the steep, grass-covered sides of a valley, down which 
a gale had blown, were directed obliquely instead of straight down 
the slope; and this was obviously due to the combined action of the 
wind and gravity.  Four castings on my lawn, where the downward 
inclination was 0  degrees 45 seconds, 1 degree, 3 degrees and 3 
degrees 30 seconds (mean 2 degrees 45 seconds) towards the north-
east, after a heavy south-west gale with rain, were divided across 
the mouths of the burrows and weighed in the manner formerly 
described.  The mean weight of the earth below the mouths of 
burrows and to leeward, was to that above the mouths and on the 
windward side as 2.75 to 1; whereas we have seen that with several 
castings which had flowed down slopes having a mean inclination of 
9 degrees 26 seconds, and with three castings where the inclination 
was above 12 degrees; the proportional weight of the earth below to 
that above the burrows was as only 2 to 1.  These several cases 
show how efficiently gales of wind accompanied by rain act in 
displacing recently ejected castings.  We may therefore conclude 
that even a moderately strong wind will produce some slight effect 
on them.

Dry and indurated castings, after their disintegration into small 
fragments or pellets, are sometimes, probably often, blown by a 
strong wind to leeward.  This was observed on four occasions, but I 
did not sufficiently attend to this point.  One old casting on a 
gently sloping bank was blown quite away by a strong south-west 
wind.  Dr. King believes that the wind removes the greater part of 
the old crumbling castings near Nice.  Several old castings on my 
lawn were marked with pins and protected from any disturbance.  
They were examined after an interval of 10 weeks, during which time 
the weather had been alternately dry and rainy.  Some, which were 
of a yellowish colour had been washed almost completely away, as 
could be seen by the colour of the surrounding ground.  Others had 
completely disappeared, and these no doubt had been blown away.  
Lastly, others still remained and would long remain, as blades of 
grass had grown through them.  On poor pasture-land, which has 
never been rolled and has not been much trampled on by animals, the 
whole surface is sometimes dotted with little pimples, through and 
on which grass grows; and these pimples consist of old worm-
castings.

In all the many observed cases of soft castings blown to leeward, 
this had been effected by strong winds accompanied by rain.  As 
such winds in England generally blow from the south and south-west, 
earth must on the whole tend to travel over our fields in a north 
and north-east direction.  This fact is interesting, because it 
might be thought that none could be removed from a level, grass-
covered surface by any means.  In thick and level woods, protected 
from the wind, castings will never be removed as long as the wood 
lasts; and mould will here tend to accumulate to the depth at which 
worms can work.  I tried to procure evidence as to how much mould 
is blown, whilst in the state of castings, by our wet southern 
gales to the north-east, over open and flat land, by looking to the 
level of the surface on opposite sides of old trees and hedge-rows; 
but I failed owing to the unequal growth of the roots of trees and 
to most pasture-land having been formerly ploughed.

On an open plain near Stonehenge, there exist shallow circular 
trenches, with a low embankment outside, surrounding level spaces 
50 yards in diameter.  These rings appear very ancient, and are 
believed to be contemporaneous with the Druidical stones.  Castings 
ejected within these circular spaces, if blown to the north-east by 
south-west winds would form a layer of mould within the trench, 
thicker on the north-eastern than on any other side.  But the site 
was not favourable for the action of worms, for the mould over the 
surrounding Chalk formation with flints, was only 3.37 inches in 
thickness, from a mean of six observations made at a distance of 10 
yards outside the embankment.  The thickness of the mould within 
two of the circular trenches was measured every 5 yards all round, 
on the inner sides near the bottom.  My son Horace protracted these 
measurements on paper; and though the curved line representing the 
thickness of the mould was extremely irregular, yet in both 
diagrams it could be seen to be thicker on the north-eastern side 
than elsewhere.  When a mean of all the measurements in both the 
trenches was laid down and the line smoothed, it was obvious that 
the mould was thickest in the quarter of the circle between north-
west and north-east; and thinnest in the quarter between south-east 
and south-west, especially at this latter point.  Besides the 
foregoing measurements, six others were taken near together in one 
of the circular trenches, on the north-east side; and the mould 
here had a mean thickness of 2.29 inches; while the mean of six 
other measurements on the south-west side was only 1.46 inches.  
These observations indicate that the castings had been blown by the 
south-west winds from the circular enclosed space into the trench 
on the north-east side; but many more measurements in other 
analogous cases would be requisite for a trustworthy result.

The amount of fine earth brought to the surface under the form of 
castings, and afterwards transported by the winds accompanied by 
rain, or that which flows and rolls down an inclined surface, no 
doubt is small in the course of a few scores of years; for 
otherwise all the inequalities in our pasture fields would be 
smoothed within a much shorter period than appears to be the case.  
But the amount which is thus transported in the course of thousands 
of years cannot fail to be considerable and deserves attention.  E. 
de Beaumont looks at the vegetable mould which everywhere covers 
the land as a fixed line, from which the amount of denudation may 
be measured. {79}  He ignores the continued formation of fresh 
mould by the disintegration of the underlying rocks and fragments 
of rock; and it is curious to find how much more philosophical were 
the views maintained long ago, by Playfair, who, in 1802, wrote, 
"In the permanence of a coat of vegetable mould on the surface of 
the earth, we have a demonstrative proof of the continued 
destruction of the rocks." {80}

Ancient encampments and tumuli.--E. de Beaumont adduces the present 
state of many ancient encampments and tumuli and of old ploughed 
fields, as evidence that the surface of the land undergoes hardly 
any degradation.  But it does not appear that he ever examined the 
thickness of the mould over different parts of such old remains.  
He relies chiefly on indirect, but apparently trustworthy, evidence 
that the slopes of the old embankments are the same as they 
originally were; and it is obvious that he could know nothing about 
their original heights.  In Knole Park a mound had been thrown up 
behind the rifle-targets, which appeared to have been formed of 
earth originally supported by square blocks of turf.  The sides 
sloped, as nearly as I could estimate them, at an angle of 45 
degrees or 50 degrees with the horizon, and they were covered, 
especially on the northern side, with long coarse grass, beneath 
which many worm-castings were found.  These had flowed bodily 
downwards, and others had rolled down as pellets.  Hence it is 
certain that as long as a mound of this kind is tenanted by worms, 
its height will be continually lowered.  The fine earth which flows 
or rolls down the sides of such a mound accumulates at its base in 
the form of a talus.  A bed, even a very thin bed, of fine earth is 
eminently favourable for worms; so that a greater number of 
castings would tend to be ejected on a talus thus formed than 
elsewhere; and these would be partially washed away by every heavy 
shower and be spread over the adjoining level ground.  The final 
result would be the lowering of the whole mound, whilst the 
inclination of the sides would not be greatly lessened.  The same 
result would assuredly follow with ancient embankments and tumuli; 
except where they had been formed of gravel or of nearly pure sand, 
as such matter is unfavourable for worms.  Many old fortifications 
and tumuli are believed to be at least 2000 years old; and we 
should bear in mind that in many places about one inch of mould is 
brought to the surface in 5 years or two inches in 10 years.  
Therefore in so long a period as 2000 years, a large amount of 
earth will have been repeatedly brought to the surface on most old 
embankments and tumuli, especially on the talus round their bases, 
and much of this earth will have been washed completely away.  We 
may therefore conclude that all ancient mounds, when not formed of 
materials unfavourable to worms, will have been somewhat lowered in 
the course of centuries, although their inclinations may not have 
been greatly changed.

Fields formerly ploughed.--From a very remote period and in many 
countries, land has been ploughed, so that convex beds, called 
crowns or ridges, usually about 8 feet across and separated by 
furrows, have been thrown up.  The furrows are directed so as to 
carry off the surface water.  In my attempts to ascertain how long 
a time these crowns and furrows last, when ploughed land has been 
converted into pasture, obstacles of many kinds were encountered.  
It is rarely known when a field was last ploughed; and some fields 
which were thought to have been in pasture from time immemorial 
were afterwards discovered to have been ploughed only 50 or 60 
years before.  During the early part of the present century, when 
the price of corn was very high, land of all kinds seems to have 
been ploughed in Britain.  There is, however, no reason to doubt 
that in many cases the old crowns and furrows have been preserved 
from a very ancient period. {81}  That they should have been 
preserved for very unequal lengths of time would naturally follow 
from the crowns, when first thrown up, having differed much in 
height in different districts, as is now the case with recently 
ploughed land.

In old pasture fields, the mould, wherever measurements were made, 
was found to be from 0.5 to 2 inches thicker in the furrows than on 
the crowns; but this would naturally follow from the finer earth 
having been washed from the crowns into the furrows before the land 
was well clothed with turf; and it is impossible to tell what part 
worms may have played in the work.  Nevertheless from what we have 
seen, castings would certainly tend to flow and to be washed during 
heavy rain from the crowns into the furrows.  But as soon as a bed 
of fine earth had by any means been accumulated in the furrows, it 
would be more favourable for worms than the other parts, and a 
greater number of castings would be thrown up here than elsewhere; 
and as the furrows on sloping land are usually directed so as to 
carry off the surface water, some of the finest earth would be 
washed from the castings which had been here ejected and be carried 
completely away.  The result would be that the furrows would be 
filled up very slowly, while the crowns would be lowered perhaps 
still more slowly by the flowing and rolling of the castings down 
their gentle inclinations into the furrows.

Nevertheless it might be expected that old furrows, especially 
those on a sloping surface, would in the course of time be filled 
up and disappear.  Some careful observers, however, who examined 
fields for me in Gloucestershire and Staffordshire could not detect 
any difference in the state of the furrows in the upper and lower 
parts of sloping fields, supposed to have been long in pasture; and 
they came to the conclusion that the crowns and furrows would last 
for an almost endless number of centuries.  On the other hand the 
process of obliteration seems to have commenced in some places.  
Thus in a grass field in North Wales, known to have been ploughed 
about 65 years ago, which sloped at an angle of 15 degrees to the 
north-east, the depth of the furrows (only 7 feet apart) was 
carefully measured, and was found to be about 4.5 inches in the 
upper part of the slope, and only 1 inch near the base, where they 
could be traced with difficulty.  On another field sloping at about 
the same angle to the south-west, the furrows were scarcely 
perceptible in the lower part; although these same furrows when 
followed on to some adjoining level ground were from 2.5 to 3.5 
inches in depth.  A third and closely similar case was observed.  
In a fourth case, the mould in a furrow in the upper part of a 
sloping field was 2.5 inches, and in the lower part 4.5 inches in 
thickness.

On the Chalk Downs at about a mile distance from Stonehenge, my son 
William examined a grass-covered, furrowed surface, sloping at from 
8 degrees to 10 degrees, which an old shepherd said had not been 
ploughed within the memory of man.  The depth of one furrow was 
measured at 16 points in a length of 68 paces, and was found to be 
deeper where the slope was greatest and where less earth would 
naturally tend to accumulate, and at the base it almost 
disappeared.  The thickness of the mould in this furrow in the 
upper part was 2.5 inches, which increased to 5 inches, a little 
above the steepest part of the slope; and at the base, in the 
middle of the narrow valley, at a point which the furrow if 
continued would have struck, it amounted to 7 inches.  On the 
opposite side of the valley, there were very faint, almost 
obliterated, traces of furrows.  Another analogous but not so 
decided a case was observed at a few miles' distance from 
Stonehenge.  On the whole it appears that the crowns and furrows on 
land formerly ploughed, but now covered with grass, tend slowly to 
disappear when the surface is inclined; and this is probably in 
large part due to the action of worms; but that the crowns and 
furrows last for a very long time when the surface is nearly level.

Formation and amount of mould over the Chalk Formation.--Worm-
castings are often ejected in extraordinary numbers on steep, 
grass-covered slopes, where the Chalk comes close to the surface, 
as my son William observed near Winchester and elsewhere.  If such 
castings are largely washed away during heavy rains, it is 
difficult to understand at first how any mould can still remain on 
our Downs, as there does not appear any evident means for supplying 
the loss.  There is, moreover, another cause of loss, namely, in 
the percolation of the finer particles of earth into the fissures 
in the chalk and into the chalk itself.  These considerations led 
me to doubt for a time whether I had not exaggerated the amount of 
fine earth which flows or rolls down grass-covered slopes under the 
form of castings; and I sought for additional information.  In some 
places, the castings on Chalk Downs consist largely of calcareous 
matter, and here the supply is of course unlimited.  But in other 
places, for instance on a part of Teg Down near Winchester, the 
castings were all black and did not effervesce with acids.  The 
mould over the chalk was here only from 3 to 4 inches in thickness.  
So again on the plain near Stonehenge, the mould, apparently free 
from calcareous matter, averaged rather less than 3.5 inches in 
thickness.  Why worms should penetrate and bring up chalk in some 
places and not in others I do not know.

In many districts where the land is nearly level, a bed several 
feet in thickness of red clay full of unworn flints overlies the 
Upper Chalk.  This overlying matter, the surface of which has been 
converted into mould, consists of the undissolved residue from the 
chalk.  It may be well here to recall the case of the fragments of 
chalk buried beneath worm-castings on one of my fields, the angles 
of which were so completely rounded in the course of 29 years that 
the fragments now resembled water-worn pebbles.  This must have 
been effected by the carbonic acid in the rain and in the ground, 
by the humus-acids, and by the corroding power of living roots.  
Why a thick mass of residue has not been left on the Chalk, 
wherever the land is nearly level, may perhaps be accounted for by 
the percolation of the fine particles into the fissures, which are 
often present in the chalk and are either open or are filled up 
with impure chalk, or into the solid chalk itself.  That such 
percolation occurs can hardly be doubted.  My son collected some 
powdered and fragmentary chalk beneath the turf near Winchester; 
the former was found by Colonel Parsons, R. E., to contain 10 per 
cent., and the fragments 8 per cent. of earthy matter.  On the 
flanks of the escarpment near Abinger in Surrey, some chalk close 
beneath a layer of flints, 2 inches in thickness and covered by 8 
inches of mould, yielded a residue of 3.7 per cent. of earthy 
matter.  On the other hand the Upper Chalk properly contains, as I 
was informed by the late David Forbes who had made many analyses, 
only from 1 to 2 per cent. of earthy matter; and two samples from 
pits near my house contained 1.3 and 0.6 per cent.  I mention these 
latter cases because, from the thickness of the overlying bed of 
red clay with flints, I had imagined that the underlying chalk 
might here be less pure than elsewhere.  The cause of the residue 
accumulating more in some places than in others, may be attributed 
to a layer of argillaceous matter having been left at an early 
period on the chalk, and this would check the subsequent 
percolation of earthy matter into it.

From the facts now given we may conclude that castings ejected on 
our Chalk Downs suffer some loss by the percolation of their finer 
matter into the chalk.  But such impure superficial chalk, when 
dissolved, would leave a larger supply of earthy matter to be added 
to the mould than in the case of pure chalk.  Besides the loss 
caused by percolation, some fine earth is certainly washed down the 
sloping grass-covered surfaces of our Downs.  The washing-down 
process, however, will be checked in the course of time; for 
although I do not know how thin a layer of mould suffices to 
support worms, yet a limit must at last be reached; and then their 
castings would cease to be ejected or would become scanty.

The following cases show that a considerable quantity of fine earth 
is washed down.  The thickness of the mould was measured at points 
12 yards apart across a small valley in the Chalk near Winchester.  
The sides sloped gently at first; then became inclined at about 20 
degrees; then more gently to near the bottom, which transversely 
was almost level and about 50 yards across.  In the bottom, the 
mean thickness of the mould from five measurements was 8.3 inches; 
whilst on the sides of the valley, where the inclination varied 
between 14 degrees and 20 degrees, its mean thickness was rather 
less than 3.5 inches.  As the turf-covered bottom of the valley 
sloped at an angle of only between 2 degrees and 3 degrees, it is 
probable that most of the 8.3-inch layer of mould had been washed 
down from the flanks of the valley, and not from the upper part.  
But as a shepherd said that he had seen water flowing in this 
valley after the sudden thawing of snow, it is possible that some 
earth may have been brought down from the upper part; or, on the 
other hand, that some may have been carried further down the 
valley.  Closely similar results, with respect to the thickness of 
the mould, were obtained in a neighbouring valley.

St. Catherine's Hill, near Winchester, is 327 feet in height, and 
consists of a steep cone of chalk about 0.25 of a mile in diameter.  
The upper part was converted by the Romans, or, as some think, by 
the ancient Britons, into an encampment, by the excavation of a 
deep and broad ditch all round it.  Most of the chalk removed 
during the work was thrown upwards, by which a projecting bank was 
formed; and this effectually prevents worm-castings (which are 
numerous in parts), stones, and other objects from being washed or 
rolled into the ditch.  The mould on the upper and fortified part 
of the hill was found to be in most places only from 2.5 to 3.5 
inches in thickness; whereas it had accumulated at the foot of the 
embankment above the ditch to a thickness in most places of from 8 
to 9.5 inches.  On the embankment itself the mould was only 1 to 
1.5 inch in thickness; and within the ditch at the bottom it varied 
from 2.5 to 3.5, but was in one spot 6 inches in thickness.  On the 
north-west side of the hill, either no embankment had ever been 
thrown up above the ditch, or it had subsequently been removed; so 
that here there was nothing to prevent worm-castings, earth and 
stones being washed into the ditch, at the bottom of which the 
mould formed a layer from 11 to 22 inches in thickness.  It should 
however be stated that here and on other parts of the slope, the 
bed of mould often contained fragments of chalk and flint which had 
obviously rolled down at different times from above.  The 
interstices in the underlying fragmentary chalk were also filled up 
with mould.

My son examined the surface of this hill to its base in a south-
west direction.  Beneath the great ditch, where the slope was about 
24 degrees, the mould was very thin, namely, from 1.5 to 2.5 
inches; whilst near the base, where the slope was only 3 degrees to 
4 degrees, it increased to between 8 and 9 inches in thickness.  We 
may therefore conclude that on this artificially modified hill, as 
well as in the natural valleys of the neighbouring Chalk Downs, 
some fine earth, probably derived in large part from worm-castings, 
is washed down, and accumulates in the lower parts, notwithstanding 
the percolation of an unknown quantity into the underlying chalk; a 
supply of fresh earthy matter being afforded by the dissolution of 
the chalk through atmospheric and other agencies.



CHAPTER VII--CONCLUSION.



Summary of the part which worms have played in the history of the 
world--Their aid in the disintegration of rocks--In the denudation 
of the land--In the preservation of ancient remains--In the 
preparation of the soil for the growth of plants--Mental powers of 
worms--Conclusion.

Worms have played a more important part in the history of the world 
than most persons would at first suppose.  In almost all humid 
countries they are extraordinarily numerous, and for their size 
possess great muscular power.  In many parts of England a weight of 
more than ten tons (10,516 kilogrammes) of dry earth annually 
passes through their bodies and is brought to the surface on each 
acre of land; so that the whole superficial bed of vegetable mould 
passes through their bodies in the course of every few years.  From 
the collapsing of the old burrows the mould is in constant though 
slow movement, and the particles composing it are thus rubbed 
together.  By these means fresh surfaces are continually exposed to 
the action of the carbonic acid in the soil, and of the humus-acids 
which appear to be still more efficient in the decomposition of 
rocks.  The generation of the humus-acids is probably hastened 
during the digestion of the many half-decayed leaves which worms 
consume.  Thus the particles of earth, forming the superficial 
mould, are subjected to conditions eminently favourable for their 
decomposition and disintegration.  Moreover, the particles of the 
softer rocks suffer some amount of mechanical trituration in the 
muscular gizzards of worms, in which small stones serve as mill-
stones.

The finely levigated castings, when brought to the surface in a 
moist condition, flow during rainy weather down any moderate slope; 
and the smaller particles are washed far down even a gently 
inclined surface.  Castings when dry often crumble into small 
pellets and these are apt to roll down any sloping surface.  Where 
the land is quite level and is covered with herbage, and where the 
climate is humid so that much dust cannot be blown away, it appears 
at first sight impossible that there should be any appreciable 
amount of sub-aerial denudation; but worm-castings are blown, 
especially whilst moist and viscid, in one uniform direction by the 
prevalent winds which are accompanied by rain.  By these several 
means the superficial mould is prevented from accumulating to a 
great thickness; and a thick bed of mould checks in many ways the 
disintegration of the underlying rocks and fragments of rock.

The removal of worm-castings by the above means leads to results 
which are far from insignificant.  It has been shown that a layer 
of earth, 0.2 of an inch in thickness, is in many places annually 
brought to the surface; and if a small part of this amount flows, 
or rolls, or is washed, even for a short distance, down every 
inclined surface, or is repeatedly blown in one direction, a great 
effect will be produced in the course of ages.  It was found by 
measurements and calculations that on a surface with a mean 
inclination of 9 degrees 26 seconds, 2.4 cubic inches of earth 
which had been ejected by worms crossed, in the course of a year, a 
horizontal line one yard in length; so that 240 cubic inches would 
cross a line 100 yards in length.  This latter amount in a damp 
state would weigh 11.5 pounds.  Thus a considerable weight of earth 
is continually moving down each side of every valley, and will in 
time reach its bed.  Finally this earth will be transported by the 
streams flowing in the valleys into the ocean, the great receptacle 
for all matter denuded from the land.  It is known from the amount 
of sediment annually delivered into the sea by the Mississippi, 
that its enormous drainage-area must on an average be lowered 
.00263 of an inch each year; and this would suffice in four and 
half million years to lower the whole drainage-area to the level of 
the sea-shore.  So that, if a small fraction of the layer of fine 
earth, 0.2 of an inch in thickness, which is annually brought to 
the surface by worms, is carried away, a great result cannot fail 
to be produced within a period which no geologist considers 
extremely long.


Archaeologists ought to be grateful to worms, as they protect and 
preserve for an indefinitely long period every object, not liable 
to decay, which is dropped on the surface of the land, by burying 
it beneath their castings.  Thus, also, many elegant and curious 
tesselated pavements and other ancient remains have been preserved; 
though no doubt the worms have in these cases been largely aided by 
earth washed and blown from the adjoining land, especially when 
cultivated.  The old tesselated pavements have, however, often 
suffered by having subsided unequally from being unequally 
undermined by the worms.  Even old massive walls may be undermined 
and subside; and no building is in this respect safe, unless the 
foundations lie 6 or 7 feet beneath the surface, at a depth at 
which worms cannot work.  It is probable that many monoliths and 
some old walls have fallen down from having been undermined by 
worms.


Worms prepare the ground {82} in an excellent manner for the growth 
of fibrous-rooted plants and for seedlings of all kinds.  They 
periodically expose the mould to the air, and sift it so that no 
stones larger than the particles which they can swallow are left in 
it.  They mingle the whole intimately together, like a gardener who 
prepares fine soil for his choicest plants.  In this state it is 
well fitted to retain moisture and to absorb all soluble 
substances, as well as for the process of nitrification.  The bones 
of dead animals, the harder parts of insects, the shells of land-
molluscs, leaves, twigs, &c., are before long all buried beneath 
the accumulated castings of worms, and are thus brought in a more 
or less decayed state within reach of the roots of plants.  Worms 
likewise drag an infinite number of dead leaves and other parts of 
plants into their burrows, partly for the sake of plugging them up 
and partly as food.

The leaves which are dragged into the burrows as food, after being 
torn into the finest shreds, partially digested, and saturated with 
the intestinal and urinary secretions, are commingled with much 
earth.  This earth forms the dark coloured, rich humus which almost 
everywhere covers the surface of the land with a fairly well-
defined layer or mantle.  Hensen {83} placed two worms in a vessel 
18 inches in diameter, which was filled with sand, on which fallen 
leaves were strewed; and these were soon dragged into their burrows 
to a depth of 3 inches.  After about 6 weeks an almost uniform 
layer of sand, a centimeter (0.4 inch) in thickness, was converted 
into humus by having passed through the alimentary canals of these 
two worms.  It is believed by some persons that worm-burrows, which 
often penetrate the ground almost perpendicularly to a depth of 5 
or 6 feet, materially aid in its drainage; notwithstanding that the 
viscid castings piled over the mouths of the burrows prevent or 
check the rain-water directly entering them.  They allow the air to 
penetrate deeply into the ground.  They also greatly facilitate the 
downward passage of roots of moderate size; and these will be 
nourished by the humus with which the burrows are lined.  Many 
seeds owe their germination to having been covered by castings; and 
others buried to a considerable depth beneath accumulated castings 
lie dormant, until at some future time they are accidentally 
uncovered and germinate.

Worms are poorly provided with sense-organs, for they cannot be 
said to see, although they can just distinguish between light and 
darkness; they are completely deaf, and have only a feeble power of 
smell; the sense of touch alone is well developed.  They can 
therefore learn but little about the outside world, and it is 
surprising that they should exhibit some skill in lining their 
burrows with their castings and with leaves, and in the case of 
some species in piling up their castings into tower-like 
constructions.  But it is far more surprising that they should 
apparently exhibit some degrees of intelligence instead of a mere 
blind instinctive impulse, in their manner of plugging up the 
mouths of their burrows.  They act in nearly the same manner as 
would a man, who had to close a cylindrical tube with different 
kinds of leaves, petioles, triangles of paper, &c., for they 
commonly seize such objects by their pointed ends.  But with thin 
objects a certain number are drawn in by their broader ends.  They 
do not act in the same unvarying manner in all cases, as do most of 
the lower animals; for instance, they do not drag in leaves by 
their foot-stalks, unless the basal part of the blade is as narrow 
as the apex, or narrower than it.


When we behold a wide, turf-covered expanse, we should remember 
that its smoothness, on which so much of its beauty depends, is 
mainly due to all the inequalities having been slowly levelled by 
worms.  It is a marvellous reflection that the whole of the 
superficial mould over any such expanse has passed, and will again 
pass, every few years through the bodies of worms.  The plough is 
one of the most ancient and most valuable of man's inventions; but 
long before he existed the land was in fact regularly ploughed, and 
still continues to be thus ploughed by earth-worms.  It may be 
doubted whether there are many other animals which have played so 
important a part in the history of the world, as have these lowly 
organized creatures.  Some other animals, however, still more lowly 
organized, namely corals, have done far more conspicuous work in 
having constructed innumerable reefs and islands in the great 
oceans; but these are almost confined to the tropical zones.



Footnotes:

{1}  'Lecons de Geologie Pratique,' tom. i. 1845, p. 140.

{2}  'Transactions Geolog. Soc.' vol. v. p. 505.  Read November 1, 
1837.

{3}  'Histoire des progres de la Geologie,' tom. i. 1847, p. 224.

{4}  'Zeitschrift fur wissenschaft.  Zoologie,' B. xxviii. 1877, p. 
361.

{5}  'Gardeners' Chronicle,' April 17, 1869, p. 418.

{6}  Mr. Darwin's attention was called by Professor Hensen to P. E. 
Muller's work on Humus in 'Tidsskrift for Skovbrug,' Band iii. Heft 
1 and 2, Copenhagen, 1878.  He had, however, no opportunity of 
consulting Muller's work.  Dr. Muller published a second paper in 
1884 in the same periodical--a Danish journal of forestry.  His 
results have also been published in German, in a volume entitled 
'Studien uber die naturlichen Humusformen, unter deren Einwirkung 
auf Vegetation und Boden,' 8vo., Berlin, 1887.

{7}  'Bidrag till Skandinaviens Oligochaetfauna,' 1871.

{8}  'Die bis jetzt bekannten Arten aus der Familie der 
Regenwurmer,' 1845.

{9}  There is even some reason to believe that pressure is actually 
favourable to the growth of grasses, for Professor Buckman, who 
made many observations on their growth in the experimental gardens 
of the Royal Agricultural College, remarks ('Gardeners' Chronicle,' 
1854, p. 619):  "Another circumstance in the cultivation of grasses 
in the separate form or small patches, is the impossibility of 
rolling or treading them firmly, without which no pasture can 
continue good."

{10}  I shall have occasion often to refer to M. Perrier's 
admirable memoir, 'Organisation des Lombriciens terrestres' in 
'Archives de Zoolog. exper.' tom. iii. 1874, p. 372.  C. F. Morren 
('De Lumbrici terrestris Hist. Nat.' 1829, p. 14) found that worms 
endured immersion for fifteen to twenty days in summer, but that in 
winter they died when thus treated.

{11}  Morren, 'De Lumbrici terrestris Hist. Nat.' &c., 1829, p. 67.

{12}  'De Lumbrici terrestris Hist. Nat.' &c., p. 14.

{13}  Histolog.  Untersuchungen uber die Regenwurmer.  'Zeitschrift 
fur wissenschaft.  Zoologie,' B. xix., 1869, p. 611.

{14}  For instance, Mr. Bridgman and Mr. Newman ('The Zoologist,' 
vol. vii. 1849, p. 2576), and some friends who observed worms for 
me.

{15}  'Familie der Regenwurmer,' 1845, p. 18.

{16}  'The Zoologist,' vol. vii. 1849, p. 2576.

{17}  'Familie der Regenwurmer,' p. 13.  Dr. Sturtevant states in 
the 'New York Weekly Tribune' (May 19, 1880) that he kept three 
worms in a pot, which was allowed to become extremely dry; and 
these worms were found "all entwined together, forming a round mass 
and in good condition."

{18}  'De Lumbrici terrestris Hist. Nat.' p. 19.

{19}  'Archives de Zoologie experimentale,' tom. vii. 1878, p. 394.  
When I wrote the above passage, I was not aware that Krukenberg 
('Untersuchungen a. d. physiol.  Inst. d. Univ.  Heidelberg,' Bd. 
ii. p. 37, 1877) had previously investigated the digestive juice of 
Lumbricus.  He states that it contains a peptic, and diastatic, as 
well as a tryptic ferment.

{20}  On the action of the pancreatic ferment, see 'A Text-Book of 
Physiology,' by Michael Foster, 2nd edit. pp. 198-203.  1878.

{21}  Schmulewitsch, 'Action des Sucs digestifs sur la Cellulose.'  
Bull. de l'Acad. Imp. de St. Petersbourg, tom. xxv. p. 549.  1879. 

{22}  Claparede doubts whether saliva is secreted by worms:  see 
'Zeitschrift fur wissenschaft.  Zoologie,' B. xix. 1869, p. 601.

{23}  Perrier, 'Archives de Zoolog. exper.' July, 1874, pp. 416, 
419.

{24}  'Zeitschrift fur wissenschaft.  Zoologie,' B. xix, 1869, pp. 
603-606.

{25}  De Vries, 'Landwirth. Jahrbucher,' 1881, p. 77.

{26}  M. Foster, 'A Text-Book of Physiology,' 2nd edit. 1878, p. 
243.

{27}  M. Foster, ut sup. p. 200.

{28}  Claparede remarks ('Zeitschrift fur wisseuschaft.  Zoolog.' 
B. 19, 1869, p. 602) that the pharynx appears from its structure to 
be adapted for suction.

{29}  An account of her observations is given in the 'Gardeners' 
Chronicle,' March 28th, 1868, p. 324.

{30}  London's 'Gard. Mag.' xvii. p. 216, as quoted in the 
'Catalogue of the British Museum Worms,' 1865, p. 327.

{31}  'Familie der Regenwurmer,' p. 19.

{32}  In these narrow triangles the apical angle is 9 degrees 34 
seconds, and the basal angles 85 degrees 13 seconds.  In the 
broader triangles the apical angle is 19 degrees 10 seconds and the 
basal angles 80 degrees 25 seconds.

{33}  See his interesting work, 'Souvenirs entomologiques,' 1879, 
pp. 168-177.

{34}  Mobius, 'Die Bewegungen der Thiere,' &c., 1873, p. 111.

{35}  'Annals and Mag. of N. History,' series ii. vol. ix. 1852, p. 
333.

{36}  'Archives de Zoolog. exper.' tom. iii. 1874, p. 405.

{37}  I state this on the authority of Semper, 'Reisen im Archipel 
der Philippinen,' Th. ii. 1877, p. 30.

{38}  Dr. King gave me some worms collected near Nice, which, as he 
believes, had constructed these castings.  They were sent to M. 
Perrier, who with great kindness examined and named them for me:  
they consisted of Perichaeta affinis, a native of Cochin China and 
of the Philippines; P. Luzonica, a native of Luzon in the 
Philippines; and P. Houlleti, which lives near Calcutta.  M. 
Perrier informs me that species of Perichaeta have been naturalized 
in the gardens near Montpellier and in Algiers.  Before I had any 
reason to suspect that the tower-like castings from Nice had been 
formed by worms not endemic in the country, I was greatly surprised 
to see how closely they resembled castings sent to me from near 
Calcutta, where it is known that species of Perichaeta abound.

{39}  'Zeitschrift fur wissenschaft.  Zoolog.'  B. xxviii. 1877, p. 
364.

{40}  'Zeitschrift fur wissenschaft.  Zoolog.' B. xxviii. 1877, p. 
356.

{41}  Perrier, 'Archives de Zoolog. exper.' tom. 3, p. 378, 1874.

{42}  This case is given in a postscript to my paper in the 
'Transact. Geolog. Soc.'  (Vol. v. p. 505), and contains a serious 
error, as in the account received I mistook the figure 30 for 80.  
The tenant, moreover, formerly said that he had marled the field 
thirty years before, but was now positive that this was done in 
1809, that is twenty-eight years before the first examination of 
the field by my friend.  The error, as far as the figure 80 is 
concerned, was corrected in an article by me, in the 'Gardeners' 
Chronicle,' 1844, p. 218.

{43}  These pits or pipes are still in process of formation.  
During the last forty years I have seen or heard of five cases, in 
which a circular space, several feet in diameter, suddenly fell in, 
leaving on the field an open hole with perpendicular sides, some 
feet in depth.  This occurred in one of my own fields, whilst it 
was being rolled, and the hinder quarters of the shaft horse fell 
in; two or three cart-loads of rubbish were required to fill up the 
hole.  The subsidence occurred where there was a broad depression, 
as if the surface had fallen in at several former periods.  I heard 
of a hole which must have been suddenly formed at the bottom of a 
small shallow pool, where sheep had been washed during many years, 
and into which a man thus occupied fell to his great terror.  The 
rain-water over this whole district sinks perpendicularly into the 
ground, but the chalk is more porous in certain places than in 
others.  Thus the drainage from the overlying clay is directed to 
certain points, where a greater amount of calcareous matter is 
dissolved than elsewhere.  Even narrow open channels are sometimes 
formed in the solid chalk.  As the chalk is slowly dissolved over 
the whole country, but more in some parts than in others, the 
undissolved residue--that is the overlying mass of red clay with 
flints,--likewise sinks slowly down, and tends to fill up the pipes 
or cavities.  But the upper part of the red clay holds together, 
aided probably by the roots of plants, for a longer time than the 
lower parts, and thus forms a roof, which sooner or later falls in, 
as in the above mentioned five cases.  The downward movement of the 
clay may be compared with that of a glacier, but is incomparably 
slower; and this movement accounts for a singular fact, namely, 
that the much elongated flints which are embedded in the chalk in a 
nearly horizontal position, are commonly found standing nearly or 
quite upright in the red clay.  This fact is so common that the 
workmen assured me that this was their natural position.  I roughly 
measured one which stood vertically, and it was of the same length 
and of the same relative thickness as one of my arms.  These 
elongated flints must get placed in their upright position, on the 
same principle that a trunk of a tree left on a glacier assumes a 
position parallel to the line of motion.  The flints in the clay 
which form almost half its bulk, are very often broken, though not 
rolled or abraded; and this may he accounted for by their mutual 
pressure, whilst the whole mass is subsiding.  I may add that the 
chalk here appears to have been originally covered in parts by a 
thin bed of fine sand with some perfectly rounded flint pebbles, 
probably of Tertiary age; for such sand often partly fills up the 
deeper pits or cavities in the chalk.

{44}  S. W. Johnson, 'How Crops Feed,' 1870, p. 139.

{45}  'Nature,' November 1877, p. 28.

{46}  'Proc. Phil. Soc.' of Manchester, 1877, p. 247.

{47}  'Trans. of the New Zealand Institute,' vol. xii., 1880, p. 
152.

{48}  Mr. Lindsay Carnagie, in a letter (June 1838) to Sir C. 
Lyell, remarks that Scotch farmers are afraid of putting lime on 
ploughed land until just before it is laid down for pasture, from a 
belief that it has some tendency to sink.  He adds:  "Some years 
since, in autumn, I laid lime on an oat-stubble and ploughed it 
down; thus bringing it into immediate contact with the dead 
vegetable matter, and securing its thorough mixture through the 
means of all the subsequent operations of fallow.  In consequence 
of the above prejudice, I was considered to have committed a great 
fault; but the result was eminently successful, and the practice 
was partially followed.  By means of Mr. Darwin's observations, I 
think the prejudice will be removed."

{49}  This conclusion, which, as we shall immediately see, is fully 
justified, is of some little importance, as the so-called bench-
stones, which surveyors fix in the ground as a record of their 
levels, may in time become false standards.  My son Horace intends 
at some future period to ascertain how far this has occurred.

{50}  Mr. R. Mallet remarks ('Quarterly Journal of Geolog. Soc.' 
vol. xxxiii., 1877, p. 745) that "the extent to which the ground 
beneath the foundations of ponderous architectural structures, such 
as cathedral towers, has been known to become compressed, is as 
remarkable as it is instructive and curious.  The amount of 
depression in some cases may be measured by feet."  He instances 
the Tower of Pisa, but adds that it was founded on "dense clay."

{51}  'Zeitschrift fur wissensch. Zoolog.' Bd. xxviii., 1877, p. 
360.

{52}  See Mr. Dancer's paper in 'Proc. Phil. Soc. of Manchester,' 
1877, p. 248.

{53}  'Lecons de Geologie pratique,' 1845, p. 142.

{54}  A short account of this discovery was published in 'The 
Times' of January 2, 1878; and a fuller account in 'The Builder,' 
January 5, 1878.

{55}  Several accounts of these ruins have been published; the best 
is by Mr. James Farrer in 'Proc. Soc. of Antiquaries of Scotland,' 
vol. vi., Part II., 1867, p. 278.  Also J. W. Grover, 'Journal of 
the British Arch. Assoc.' June 1866.  Professor Buckman has 
likewise published a pamphlet, 'Notes on the Roman Villa at 
Chedworth,' 2nd edit. 1873 Cirencester.

{56}  These details are taken from the 'Penny Cyclopaedia,' article 
Hampshire.

{57}  "On the denudation of South Wales," &c., 'Memoirs of the 
Geological Survey of Great Britain,' vol. 1., p. 297, 1846.

{58}  'Geological Magazine,' October and November, 1867, vol.  iv.  
pp.  447 and 483.  Copious references on the subject are given in 
this remarkable memoir.

{59}  A. Tylor "On changes of the sea-level," &c., ' Philosophical 
Mag.' (Ser. 4th) vol. v., 1853, p. 258.  Archibald Geikie, 
Transactions Geolog. Soc. of Glasgow, vol. iii., p. 153 (read 
March, 1868).  Croll "On Geological Time," 'Philosophical Mag.,' 
May, August, and November, 1868.  See also Croll, 'Climate and 
Time,' 1875, Chap. XX.  For some recent information on the amount 
of sediment brought down by rivers, see 'Nature,' Sept.  23rd, 
1880.  Mr. T. Mellard Reade has published some interesting articles 
on the astonishing amount of matter brought down in solution by 
rivers.  See Address, Geolog. Soc., Liverpool, 1876-77.

{60}  "An account of the fine dust which often falls on Vessels in 
the Atlantic Ocean," Proc. Geolog. Soc. of London, June 4th, 1845.

{61}  For La Plata, see my 'Journal of Researches,' during the 
voyage of the Beagle, 1845, p. 133.  Elie de Beaumont has given 
('Lecons de Geolog. pratique,' tom. I. 1845, p. 183) an excellent 
account of the enormous quantity of dust which is transported in 
some countries.  I cannot but think that Mr. Proctor has somewhat 
exaggerated ('Pleasant Ways in Science,' 1879, p. 379) the agency 
of dust in a humid country like Great Britain.  James Geikie has 
given ('Prehistoric Europe,' 1880, p. 165) a full abstract of 
Richthofen's views, which, however, he disputes.

{62}  These statements are taken from Hensen in 'Zeitschrift fur 
wissenschaft. Zoologie.' Bd. xxviii., 1877, p. 360.  Those with 
respect to peat are taken from Mr. A. A. Julien in 'Proc. American 
Assoc. Science,' 1879, p. 354.

{63}  I have given some facts on the climate necessary or 
favourable for the formation of peat, in my 'Journal of 
Researches,' 1845, p. 287.

{64}  A. A. Julien "On the Geological action of the Humus-acids," 
'Proc. American Assoc. Science,' vol.  xxviii., 1879, p. 311.  Also 
on "Chemical erosion on Mountain Summits;" 'New York Academy of 
Sciences,' Oct. 14, 1878, as quoted in the 'American Naturalist.'  
See also, on this subject, S. W. Johnson, 'How Crops Feed,' 1870, 
p. 138.

{65}  See, for references on this subject, S. W. Johnson, 'How 
Crops Feed,' 1870, p. 326.

{66}  This statement is taken from Mr. Julien, 'Proc. American 
Assoc. Science,' vol.  xxviii., 1879, p. 330.

{67}  The preservative power of a layer of mould and turf is often 
shown by the perfect state of the glacial scratches on rocks when 
first uncovered.  Mr. J. Geikie maintains, in his last very 
interesting work ('Prehistoric Europe,' 1881), that the more 
perfect scratches are probably due to the last access of cold and 
increase of ice, during the long-continued, intermittent glacial 
period.

{68}  Many geologists have felt much surprise at the complete 
disappearance of flints over wide and nearly level areas, from 
which the chalk has been removed by subaerial denudation.  But the 
surface of every flint is coated by an opaque modified layer, which 
will just yield to a steel point, whilst the freshly fractured, 
translucent surface will not thus yield.  The removal by 
atmospheric agencies of the outer modified surfaces of freely 
exposed flints, though no doubt excessively slow, together with the 
modification travelling inwards, will, as may be suspected, 
ultimately lead to their complete disintegration, notwithstanding 
that they appear to be so extremely durable.

{69}  'Archives de Zoolog. exper.' tom. iii. 1874, p. 409.

{70}  'Nouvelles Archives du Museum,' tom. viii. 1872, pp.  95, 
131.

{71}  Morren, in speaking of the earth in the alimentary canals of 
worms, says, "praesepe cum lapillis commixtam vidi:" 'De Lumbrici 
terrestris Hist. Nat.' &c., 1829, p. 16.

{72}  Perrier, 'Archives de Zoolog. exper.' tom. iii. 1874, p. 419.

{73}  Morren, 'De Lumbrici terrestris Hist. Nat.' &c., p. 16.

{74}  'Archives de Zoolog. exper.' tom. iii. 1874, p. 418.

{75}  This conclusion reminds me of the vast amount of extremely 
fine chalky mud which is found within the lagoons of many atolls, 
where the sea is tranquil and waves cannot triturate the blocks of 
coral.  This mud must, as I believe ('The Structure and 
Distribution of Coral-Reefs,' 2nd edit. 1874, p. 19), be attributed 
to the innumerable annelids and other animals which burrow into the 
dead coral, and to the fishes, Holothurians, &c., which browse on 
the living corals.

{76}  Anniversary Address:  'The Quarterly Journal of the 
Geological Soc.' May 1880, p. 59.

{77}  Mr. James Wallace has pointed out that it is necessary to 
take into consideration the possibility of burrows being made at 
right angles to the surface instead of vertically down, in which 
case the lateral displacement of the soil would be increased.

{78}  'Elements of Geology,' 1865, p. 20.

{79}  'Lecons de Geologie pratique, 1845; cinquieme Lecon.  All 
Elie de Beaumont's arguments are admirably controverted by Prof. A. 
Geikie in his essay in Transact. Geolog. Soc. of Glasgow, vol. iii. 
p. 153, 1868.

{80}  'Illustrations of the Huttonian Theory of the Earth,' p. 107.

{81}  Mr. E. Tylor in his Presidential address ('Journal of the 
Anthropological Institute,' May 1880, p. 451) remarks:  "It appears 
from several papers of the Berlin Society as to the German 'high-
fields' or 'heathen-fields' (Hochacker, and Heidenacker) that they 
correspond much in their situation on hills and wastes with the 
'elf-furrows' of Scotland, which popular mythology accounts for by 
the story of the fields having been put under a Papal interdict, so 
that people took to cultivating the hills.  There seems reason to 
suppose that, like the tilled plots in the Swedish forest which 
tradition ascribes to the old 'hackers,' the German heathen-fields 
represent tillage by an ancient and barbaric population."

{82}  White of Selborne has some good remarks on the service 
performed by worms in loosening, &c., the soil.  Edit, by L. 
Jenyns, 1843, p. 281.

{83}  'Zeitschrift fur wissenschaft. Zoolog.' B. xxviii. 1877, p. 
360.