f direction in snails is located at the base of
the cephalic ganglion (brain); this ganglion lies immediately between
and below the "horns" (eye-stalks), and is composed of several
circumscribed and well-marked accumulations or corpuscles of nerve-cells
and nerve-filaments.

This sense centre can easily be destroyed without inflicting injury on
the circumjacent sense centres. Whenever this is done, the snail loses
its sense of direction and locality, and cannot find its way back to its
home when it is carried thence, and deposited amid new surroundings. It
is not killed by the mutilation, for I have seen marked snails in which
this sense centre had been destroyed, alive and apparently in good
health, several weeks after having undergone this operation; they found
temporary homes wherever they chanced to be.

The limpet is likewise a homing animal, and invariably returns to its
home after journeys in search of food. Lieutenant L----, an officer in
the British navy, once told me that he had repeatedly had specimens of
this animal under observation for months at a time, and that they always
had particular spots, generally depressions in rocks, which they
regarded as homes, to which they would always return after excursions in
search of sustenance. Romanes makes a similar statement.[103]

[103] _Animal Intelligence_, pp. 28, 29.

Some beetles have their homing sense highly developed; thus, in Mammoth
Cave, the blind beetle (_Adelops_) has its particular home, and will
always return to it even when it is set free at a considerable distance.
Notwithstanding the fact these insects are blind, and that darkness
reigns in this immense cavern, they have periods of rest corresponding
with the diurnal rest-periods of kindred species living in daylight;
hence, it is easy to study their habits at home and abroad.

I have frequently marked these beetles and then set them free some
distance away from their domiciles; they would hide themselves at once
beneath stones or clods of earth, but as soon as they had recovered from
their fright they would turn towards home, and would not stop, if left
unmolested, until they arrived at their particular and individual homing
places. Truly a most wonderful exhibition of the homing sense!

At first, these beetles are, probably, directed and governed by their
sense of direction alone, but as soon as they arrive among familiar
surroundings, memory comes to their aid.

The agile flea is anothe