which is the really essential part of the process, and we cannot
afford, with Moll, to ignore it altogether.

Wallace opposed Darwin's theory of sexual selection, but it can scarcely
be said that his attitude toward it bears critical examination. On the one
hand, as has already been noted, he saw but one side of that theory and
that the unessential side, and, on the other hand, his own view really
coincided with the more essential elements in Darwin's theory. In his
_Tropical Nature_ he admitted that the male's "persistency and energy win
the day," and also that this "vigor and liveliness" of the male are
usually associated with intense coloration, while twenty years later (in
his _Darwinism_) he admitted also that it is highly probable that the
female is pleased or excited by the male's display. But all that is really
essential in Darwin's theory is involved, directly or indirectly, in these
admissions.

Espinas, in 1878, in his suggestive book, _Des Sociétés Animales_,
described the odors, colors and forms, sounds, games, parades, and mock
battles of animals, approaching the subject in a somewhat more
psychological spirit than either Darwin or Wallace, and he somewhat more
clearly apprehended the object of these phenomena in producing mutual
excitement and stimulating tumescence. He noted the significance of the
action of the hermaphroditic snails in inserting their darts into each
other's flesh near the vulva in order to cause preliminary excitation. He
remarks of this whole group of phenomena: "It is the preliminary of sexual
union, it constitutes the first act of it. By it the image of the male is
graven on the consciousness of the female, and in a manner impregnates it,
so as to determine there, as the effects of this representation descend to
the depths of the organism, the physiological modifications necessary to
fecundation." Beaunis, again, in an analysis of the sexual sensations, was