the formation of vegetable mould-第16章
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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
