to believe that fear and joy, anger and desire, certain
powers of perception and inference, are in their minds similar to
our own. But fear in a fish is certainly a much dimmer apprehension
of danger than in us, even if it deserves the name of apprehension.
And the mental state which we call "alarm" in a fly or any lower
animal is very difficult to clearly imagine or at all express in
terms of our own mind.

Some investigators have made the mistake of projecting into the
animal mind all our emotions and complicated trains of thought. Thus
Schwammerdam apparently credits the snail with remorse for the
commission of excesses. Others go to the other extreme and make
animals hardly more than mindless automata. We are warned,
therefore, by our very mode of study, to be cautious, not too
absolutely sure of our results, nor indignant at others who may take
a very different view. And yet by moving cautiously and accepting
only what seems fairly clear and evident we may arrive at very
valuable and tolerably sure results.

The human mind, and the animal mind apparently, manifests itself in
three states or functions. These are intelligence, the realm of
knowledge; susceptibility, the realm or state of feelings or
emotions; will, the power or state of choice. Let us trace first the
development of intelligence or the intellect in the animal. Let us
try to discover what kinds of knowledge are successively attained
and the mode and sequence of their attainment. Hydra appears to be
conscious of its food. It recognizes it partially by touch, perhaps
also by feeling the waves caused by its approach. It seems also to
recognize food at a little distance by a power comparable to our
sense of smell. Stronger impacts cause it to contract. It neither
sees nor hears; it probably does little or no thinking. Its
knowledge is therefore limited to the recognition of objects either
in contact with, or but slightly removed from, itself. And its
recognition of the objects is very dim and incomplete, obtained
through the sense of touch and smell.

A little higher in the animal world a rude ear has developed, first
as a very delicate organ for feeling the waves caused by approaching
food or enemies; only later as an organ of hearing. Meanwhile the
eye has been developing, to perceive the subtle ether vibrations.
The eye of the turbellaria distinguishes only light from darkness,
that of the annelid is a true visual organ. Now the brain can begin
to