It must be remembered that fear is an element liable to arise in all courtship on one side or the other. It is usually on the side of the female, but not invariably. Among spiders, for instance, it is usually the male who feels fear, and very reasonably, for he is much weaker than the female. "Courtship by the male spider" says T.H. Montgomery ("The Courtship of Araneads," _American Naturalist_, March, 1910, p. 166), "results from a combination of the state of desire for and fear of the female." It is by his movements of fear that he advertises himself to the female as a male, and it is by the same movements that he is unconsciously impelled to display prominently his own ornamentation. We are thus brought to those essential facts of primitive courtship with which we started. But we are now able to understand more clearly how it is that alien emotional states became abnormally associated with the sexual life. Normally the sexual impulse is sufficiently reinforced by the ordinary active energies of the organism which courtship itself arouses, energies which, while they may be ultimately in part founded on anger and fear, rarely allow these emotions to be otherwise than latent. Motion, it may be said, is more prominent than emotion. Even normally a stimulant to emotional activities is pleasurable, just as motion itself is pleasurable. It may even be useful, as was noted long ago by Erasmus Darwin; he tells of a friend of his who, when painfully fatigued by riding, would call up ideas arousing indignation, and thus relieve the fatigue, the indignation, as Darwin pointed out, increasing muscular activity.[136]