which more extended and precise results will in the future be probably
found.

In his famous _Descent of Man_, wherein he first set forth the doctrine of
sexual selection, Darwin injured an essentially sound principle by
introducing into it a psychological confusion whereby the physiological
sensory stimuli through which sexual selection operates were regarded as
equivalent to æsthetic preferences. This confusion misled many, and it is
only within recent years (as has been set forth in the "Analysis of the
Sexual Impulse" in the previous volume of these _Studies_) that the
investigations and criticisms of numerous workers have placed the doctrine
of sexual selection on a firm basis by eliminating its hazardous æsthetic
element. Love springs up as a response to a number of stimuli to
tumescence, the object that most adequately arouses tumescence being that
which evokes love; the question of æsthetic beauty, although it develops
on this basis, is not itself fundamental and need not even be consciously
present at all. When we look at these phenomena in their broadest
biological aspects, love is only to a limited extent a response to beauty;
to a greater extent beauty is simply a name for the complexus of stimuli
which most adequately arouses love. If we analyze these stimuli to
tumescence as they proceed from a person of the opposite sex we find that
they are all appeals which must come through the channels of four senses:
touch, smell, hearing, and, above all, vision. When a man or a woman
experiences sexual love for one particular person from among the multitude
by which he or she is surrounded, this is due to the influences of a group
of stimuli coming through the channels of one or more of these senses.
There has been a sexual selection conditioned by sensory stimuli. This is
true even of the finer and more spiritual influences that proceed from one
person to another, although, in order to grasp the phenomena adequately,
it is best to insist on the more fundamental and less complex forms which