The human animal manifests an excess in sex-attraction which not only injures the race through its morbid action on the natural processes of reproduction, but which injures the happiness of the individual through its morbid reaction on his own desires. What is the cause of this excessive sex-attraction in the human species? The immediately acting cause of sex-attraction is sex-distinction. The more widely the sexes are differentiated, the more forcibly they are attracted to each other. The more highly developed becomes the distinction of sex in either organism, the more intense is its attraction for the other. In the human species we find sex-distinction carried to an excessive degree. Sex-distinction in humanity is so marked as to retard and confuse race-distinction, to check individual distinction, seriously to injure the race. Accustomed as we are simply to accept the facts of life as we find them, to consider people as permanent types instead of seeing them and the whole race in continual change according to the action of many forces, it seems strange at first to differentiate between familiar manifestations of sex-distinction, and to say: “This is normal, and should not be disturbed. This is abnormal, and should be removed.” But that is precisely what must be done. Normal sex-distinction manifests itself in all species in what are called primary and secondary sex-characteristics. The primary are those organs and functions essential to reproduction; the secondary, those modifications of structure and function which subserve the uses of reproduction ultimately, but are not directly essential,—such as the horns of the stag, of use in sex-combat; the plumage of the peacock, of use in sex-competition. All the minor characteristics of beard or mane, comb, wattles, spurs, gorgeous color or superior size, which distinguish the male from the female,—these are distinctions of sex. These distinctions are of use to the species through reproduction only, the processes of race-preservation. They are not of use in self-preservation. The creature is not profited personally by his mane or crest or tail-feathers: they do not help him get his dinner or kill his enemies.