“It is clear,” continues Darwin, “that these characters are the result of sexual and not of ordinary selection, since unarmed, unornamented, or unattractive males would succeed equally well in the battle for life and in leaving a numerous progeny, but for the presence of better-endowed males. We may infer that this would be the case, because the females, which are unarmed and unornamented, are able to survive and procreate their kind. . . . Just as man can improve the breed of his game-cocks by the selection of those birds which are victorious in the cockpit, so it appears that the strongest and most vigorous males, or those provided with the best weapons, have prevailed under nature, and have led to the improvement of the natural breed or species.” Selection by Females “With mammals,” says Darwin (_loc. cit._, p. 763), “the male appears to win the female much more through the law of battle than through the display of his charms.” In the case of birds, however, feminine preference comes more into play. It is well known that cocks display their charms to the hens at the breeding season, and Darwin believed that the hen selected the most beautiful of her rival suitors. “Just as man,” he writes (p. 326 of _The Descent of Man_, new edition, 1901), “can give beauty, according to his standard of taste, to his male poultry, or, more strictly, can modify the beauty originally acquired by the parent species, can give to the Sebright bantam a new and elegant plumage, an erect and peculiar carriage, so it appears that female birds in a state of nature have, by a long selection of the more attractive males, added to their beauty or other attractive qualities.” Thus the theory of sexual selection is based on three assumptions. Firstly, that there is in all species competition among the males for females with which to mate. Secondly, that this results in either “the law of battle” among the males, or selection by the female of one among several admirers. Thirdly, that the female selects, as a rule, the most attractive of her suitors. The evidence upon which Darwin founds this theory may be thus summarised:— 1. In cases where the sexes differ in appearance, or power of song, it is almost invariably the cock who is the more beautiful or the better singer, as the case may be. 2. All male birds that possess accessory plumes or other attractions, make a most elaborate display of these before the females at the mating season, hence “it is obviously probable that these appreciate the beauty of their suitors.” 3. Darwin was able to cite specific instances in which the hens showed preference.