what Hoffmeister says that a light will occasionally cause paired
individuals to separate.

When a worm is suddenly illuminated and dashes like a rabbit into
its burrow--to use the expression employed by a friend--we are at
first led to look at the action as a reflex one. The irritation of
the cerebral ganglia appears to cause certain muscles to contract
in an inevitable manner, independently of the will or consciousness
of the animal, as if it were an automaton. But the different
effect which a light produced on different occasions, and
especially the fact that a worm when in any way employed and in the
intervals of such employment, whatever set of muscles and ganglia
may then have been brought into play, is often regardless of light,
are opposed to the view of the sudden withdrawal being a simple
reflex action. With the higher animals, when close attention to
some object leads to the disregard of the impressions which other
objects must be producing on them, we attribute this to their
attention being then absorbed; and attention implies the presence
of a mind. Every sportsman knows that he can approach animals
whilst they are grazing, fighting or courting, much more easily
than at other times. The state, also, of the nervous system of the
higher animals differs much at different times, for instance, a
horse is much more readily startled at one time than at another.
The comparison here implied between the actions of one of the
higher animals and of one so low in the scale as an earth-worm, may
appear far-fetched; for we thus attribute to the worm attention and
some mental power, nevertheless I can see no reason to doubt the
justice of the comparison.

Although worms cannot be said to possess the power of vision, their