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.
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