The males of carnivorous animals are already well armed; though to them and to others, special means of defence may be given through means of sexual selection, as the mane of the lion, and the hooked jaw to the male salmon; for the shield may be as important for victory as the sword or spear.
Among birds, the contest is often of a more peaceful character.

All those who have attended to the subject, believe that there is the severest rivalry between the males of many species to attract, by singing, the females.

The rock-thrush of Guiana, birds of paradise, and some others, congregate, and successive males display with the most elaborate care, and show off in the best manner, their gorgeous plumage; they likewise perform strange antics before the females, which, standing by as spectators, at last choose the most attractive partner.

Those who have closely attended to birds in confinement well know that they often take individual preferences and dislikes: thus Sir R.Heron has described how a pied peacock was eminently attractive to all his hen birds.

I cannot here enter on the necessary details; but if man can in a short time give beauty and an elegant carriage to his bantams, according to his standard of beauty, I can see no good reason to doubt that female birds, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect.