The evolution of sex / by Professor Patrick Geddes and J. Arthur Thomson.

  • Patrick Geddes
Date:
[1900]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The evolution of sex / by Professor Patrick Geddes and J. Arthur Thomson. Source: Wellcome Collection.

    43/366 (page 23)
    THE SEXES, AND CRITICISM OF SEXUAL SELECTION. 23 secondary sexual characters as part and parcel of the sexual diathesis, — as expressions for the most part of exuberant maleness. Secondly, when the reproductive organs are removed by castration, the secondary sexual characters tend to remain undeveloped. Thus, as Darwin notes, stags never renew their antlers after castration, though normally of course they renew them each breeding season. The reindeer, where the horns occur on the females as well, is an interesting excep¬ tion to the rule, for after castration the male still renews the growth. This however merely indicates that the originally sexual characters have become organised into the general life of the body. In sheep, antelopes, oxen, &c., castration modifies or reduces the horns ; and the same is true of odoriferous glands. The parasitic crustacean Sacculina has been shown by Delage to effect a partial castration of the crabs to which it fixes itself, and the same has been observed by Giard in other cases. In two such cases an approximation to the female form of appendage has been observed. Lastly, in aged females, which have ceased to be functional in reproduction, the minor peculiarities of their sex often disappear, and they become liker males, both in structure and habits,—witness the familiar case of crowing hens. From the presupposition, then, of the intimate connection between the sexuahty and the secondary characters (which is indeed everywhere allowed), it is possible to advance a step further. Thus in regard to colour, that the male is usually brighter than the female is an acknowledged fact. But pig¬ ments of many kinds are physiologically regarded as of the nature of waste products. Such for instance is the guanin, so abundant on the skin of fishes and some other animals. Abundance of such pigments, and richness of variety in related series, point to pre-eminent activity of chemical processes in the animals which possess them. Technically expressed, abundant pigments are expressions of intense metabolism. But pre¬ dominant activity has been already seen to be characteristic of the male sex ; these bright colours, then, are often natural to maleness. In a literal_sense animals put on beauty for a^h^s. and the males more so because they are males, and not_ prim,nrj]y for any nther renson whatever._ We are well aware tKat^in spite of the researches of Krüllenberg, Sorby, MacMunn, and others, our knowledge of the physiology of many of the pigments is still very scanty. Yet in many cases, alike among