While we have these various and to some extent conflicting elements in a man's ideal of feminine beauty, the question is still further complicated by the fact that sexual selection in the human species is not merely the choice of the woman by the man, but also the choice of the man by the woman. And when we come to consider this we find that the standard is altogether different, that many of the elements of beauty as it exists in woman for man have here fallen away altogether, while a new and preponderant element has to be recognized in the shape of a regard for strength and vigor. This, as I have pointed out, is not a purely visual character, but a tactile pressure character translated into visual terms. When we have stated the sexual ideal we have not yet, however, by any means stated the complete problem of human sexual selection. The ideal that is desired and sought is, in a large measure, not the outcome of experience; it is not even necessarily the expression of the individual's temperament and idiosyncrasy. It may be largely the result of fortuitous circumstances, of slight chance attractions in childhood, of accepted traditions consecrated by romance. In the actual contacts of life the individual may find that his sexual impulse is stirred by sensory stimuli which are other than those of the ideal he had cherished and may even be the reverse of them. Beyond this, also, we have reason for believing that factors of a still more fundamentally biological character, to some extent deeper even than all these psychic elements, enter into the problem of sexual selection. Certain individuals, apart altogether from the question of whether they are either ideally or practically the most fit mates, display a greater energy and achieve a greater success than others in securing partners. These individuals possess a greater constitutional vigor, physical or mental, which conduces to their success in practical affairs generally, and probably also heightens their specifically philogamic activities.