SEXUAL SELECTION (Lat. segta/is, re lating to sex, from serifs, secus, sex). This prin ciple depends, as Darwin states, not on a strug gle for existence, but on a struggle between the males for possession of the females. The result is not death to the unsuccessful competitor, but few or no offspring. In many cases, however. victory depends not on general vigor, but on the possession of special weapons confined to the male sex, as the spurs of the cock or the horns of the stag.
The war is perhaps severest between the males of polygamous animals, and these seem oftenest provided with special weapons of offense. Among birds the contest is often less gross and fierce, the males rivaling each other in attracting the females by their powers of song or display of plumage. Darwin concludes "that when the males and females of any animal have the same habits of life, but differ in structure, color, or ornament, such differences have been mainly caused by sexual selection; that is, by individual males having had, in successive generations, some slight advantage over other males. in their
means of defense, or charms, and hav ing transmitted these advantages to their male offspring." Although Wallace does not accept the theory of sexual selection, claiming that bright colors were originally normal in both sexes. but have been eliminated in the females, yet the facts seem to substantiate the views of Darwin. As observed by Romaues. it is "a theory wholly and completely distinct from the theory of natural selection." Pan.iooatAPnY. Darwin, Origin of Species (6th ed., London, 1S82) : The Descent of Man and Selection in. Relation to Sex (2d ed., Loudon, 1874) ; Wallace, Darwinism (London, 1889) ; 0. W. and E. 0. Peckham, Sexual Selection in Spiders (Milwaukee, 1890).