e or less
independent discharge, omitting all reference to the loading of
the gun. The essential elements are the loading and the
discharging. Contrectation is a part of loading, though not a
necessary part, since the loading may be effected mechanically.
But to understand the process of firing a gun and to comprehend
the mechanism of the discharge, we must insist on the act of
loading and not merely on the contact of the hand. So it is in
analyzing the sexual impulse. Contrectation is indeed highly
important, but it is important only in so far as it aids
tumescence, and so may be subordinated to tumescence, exactly as
it may also be subordinated to detumescence. It is tumescence
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 Societes 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 determ