manner in which the species of Perich ta 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 {33} 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 {34} 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. {35a} But they
live chiefly on half-decayed leaves; and these would be useless to them
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