ocess
of evolution. I refer to the sense of direction, or "homing instinct,"
so-called, which will be treated at length in the chapter on Auxiliary
Senses.

Darwin has very beautifully demonstrated the senses of touch, taste, and
smell in the angle-worm; provisionally he denies it, however, the senses
of sight and hearing.[32] I think he is in error as to these last two
senses.

[32] Darwin, _Formation of Vegetable Mould_.

Angle-worms are nocturnal in their habits, hence, we should expect, from
the very nature of things, to find them able to differentiate between
light and darkness. And experiments show, very conclusively, that they
are very sensitive to light. My vermicularium is made of glass,
consequently, when one of its inmates happens to be next to the glass
sides, which very frequently occurs, it is easy to experiment on it with
pencils of strong light. If a ray of light is directed upon an
angle-worm, it at once begins to show discomfort, and, in a very few
moments, it will crawl away from the source of annoyance, and hide in
some tunnel deep in the earth of the vermicularium. Again, when the
worms are out of their tunnels at night, a strong light shining on them
will at once cause them to seek their holes.

If the back of an earthworm be examined with a high-power lens (x500),
small points of pigment will be seen here and there in its dorsal
integument; these, I believe, are primitive eyes (ocelli). I think that
the worm is enabled to tell the difference between light and darkness
through the agency of these minute dark spots, which serve to arrest the
rays of light, thus conveying a stimulus to nerve-fibrils, which, in
turn, carry it to the sensorium.

Any country schoolboy will tell you that worms can hear. He points to
his simple experiment (pounding on the earth with a club) in proof of
his assertion. For, as soon as he begins to pound the ground in a
favorable neighborhood, the worms will come to the surface "to see what
makes the noise." Darwin assumes that the worms feel the vibrations,
which are disagreeable to them, and come to the surface in order to
escape them. I do not deny the possibility or the probability of this
assumption; I do deny, however, that it proves that worms are deaf.

If the third anal segment (abdominal aspect) of a worm be examined, two
round, disk-like organs incorporated in the integument will be found;
these organs are supplied with special nerves which lead to the ce