Now, if we remove the generative organs—the origin of sexual activity—we leave an animal purely vegetative, and one in which none, or hardly any, of the secondary sexual characters will make their appearance. They are not then part of the essential vegetative basis of the animal, but a mere expression of its sex. Remove the sex, and we remove them also. Can it then be said that they are hereditary, even although the sexual activity from which they arise be so? I suggest that they are not, although their partial appearance in some cases, even after the destruction of the generative organs (if not due to an imperfect destruction), would seem to show that perhaps they may eventually, after many generations, become so.
What I conceive to happen is somewhat as follows:—In animals which exhibit neither sexual dimorphism nor seasonal armature or ornamentation, the influence of the generative organs is exerted equally upon the sexes, as well as, probably, throughout life. In animals exhibiting the phenomenon either of sexual dimorphism or seasonal armature or ornamentation, the generative organs, when the individual is young, have usually little or no influence on the body, which follows in its growth the simplest possible laws. As soon, however, as the generative organs commence to grow, their influence is usually very marked. Their increase—often sudden, and, one might almost say, violent—is effected at the expense of the other organs, which, as in the case of the muscles of the Salmon, are actually robbed of their material. The whole metabolism of the body is disturbed, and the nervous system is particularly affected. The pigment and material thus set loose is not necessarily transferred in its entirety to the genitalia, but may, as in the case of Oncorhynchus, find its way to the skin or elsewhere. I have suggested that in some such cases the condition of the animal is purely pathological. The heightened coloration is, as in the human jaundice, the mere outward manifestation of disease—a disease to which, in this case, the animal eventually succumbs. There must, however, be numerous cases where the animal, although sickening, survives. It is here that the power of Natural or Sexual Selection supervenes as a guiding influence on the manner and direction of the transference of pigment and matter. This matter, at first transferred haphazard, is guided into
