the formation of vegetable mould-第5章
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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
