necessary to clean the latter, and the fish were taken out. They
were of a dusky drab color when first taken out, but soon regained their
vivid tints when placed in a white vessel containing clear water. They
had evidently changed color in order to harmonize with the black walls
and bottom of the cistern.

Certain katydids are marked tinctumutants. I took one from the dark
foliage of an elm and placed her on the lighter-colored leaves of a
locust. She could be easily seen when first placed on the locust; in a
few moments, however, she had faded to such an extent that she was
barely noticeable.

The larvae of certain moths, beetles, and butterflies also possess the
chromatophoric function. The chromatophores in the larva of _Vanessa_
are very numerous, and this grub is a remarkably successful
tinctumutant; the same can be said of the larvae of certain varieties of
_Pieris_.

The power of changing color so as to resemble, in coloring, surrounding
objects is evidently one of Nature's weapons of defence. In some animals
it is developed in a wonderful manner. Wherever it is found it becomes
to the animal possessing it a powerful means of defence by rendering it
inconspicuous, and in some instances wholly unnoticeable.

After nine years of careful, systematic, and painstaking investigation,
I am prepared to affirm that, besides the senses, sight, smell, taste,
touch, hearing, and tinctumutation, certain animals have yet another
sense, the sense of locality, or of direction, commonly called the
"homing instinct." This remarkable function of the mind is not an
instinct any more than the sense of sight or smell is an instinct, but
is, on the contrary, a true sense; for I have demonstrated by actual
experiment that it has a centre in the brains (ganglia) of some of the
animals possessing it, just as the other senses have their centres. And,
since this centre has been found in certain species, and that, too, in
creatures very low in the scale of animal life, it is reasonable to
infer that it is present in the brains (ganglia) of all those animals
which evince the so-called "homing instinct."

In the process of civilization certain of the five senses in man become
dull and blunted; thus, the sense of smell in the Tagals of the
Philippine Islands is much more acute than it is in the civilized
European, and what is true of the sense of smell is also true of the
other senses, save that of touch, in all primitive peoples. This las