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, {93} 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
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