seized the toad by one of its legs and drew it out of the hole. The
instincts of even the higher animals are often followed in a senseless or
purposeless manner: the weaver-bird will perseveringly wind threads
through the bars of its cage, as if building a nest: a squirrel will pat
nuts on a wooden floor, as if he had just buried them in the ground: a
beaver will cut up logs of wood and drag them about, though there is no
water to dam up; and so in many other cases.
Mr. Romanes, who has specially studied the minds of animals, believes
that we can safely infer intelligence, only when we see an individual
profiting by its own experience. By this test the cobra showed some
intelligence; but this would have been much plainer if on a second
occasion he had drawn a toad out of a hole by its leg. The Sphex failed
signally in this respect. Now if worms try to drag objects into their
burrows first in one way and then in another, until they at last succeed,
they profit, at least in each particular instance, by experience.
But evidence has been advanced showing that worms do not habitually try
to draw objects into their burrows in many different ways. Thus
half-decayed lime-leaves from their flexibility could have been drawn in
by their middle or basal parts, and were thus drawn into the burrows in
considerable numbers; yet a large majority were drawn in by or near the
apex. The petioles of the Clematis could certainly have been drawn in
with equal ease by the base and apex; yet three times and in certain
cases five times as many were drawn in by the apex as by the base. It
might have been thought that the foot-stalks of leaves would have tempted
the worms as a convenient handle; yet they are not largely used, except
when the base of the blade is narrower than the apex. A large number of
the petioles of the ash are drawn in by the base; but this part serves
the worms as food. In the case of pine-leaves worms plainly show that
they at least do not seize the leaf by chance; but their choice does not
appear to be determined by the divergence of the two needles, and the
consequent advantage or necessity of drawing them into their burrows by
the base. With respect to the triangles of paper, those which had been
drawn in by the apex rarely had their bases creased or dirty; and this
shows that the worms had not often first tried to drag them in by this
end.
If worms are able to judge, either before drawing or after having drawn
an object close to the mouths of their burrows, how best to drag it in,
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