A DIFFERENCE IN THE METABOLISM OF THE SEXES 39
advanced the opposite view, that the female owes her soberness to the fact that only inconspicuous females have in the struggle for existence escaped destruction during the breeding season. There are fatal objections to both these theories ; and, taking his cue from Tylor, 1 Wallace himself, in a later work, suggested the true explanation, namely, that the superior variability of the male is constitutional, and due to general laws of growth and development. "If ornament," he says, "is the natural product and direct outcome of superabundant health and vigor, then no other mode of selection is needed to account for the presence of such ornament." 2 That a tendency to spend energy more rapidly should result in more striking morphological variation is to be expected ; or, put otherwise, the fact of a greater varia- tional tendency in the male is the outcome of a constitutional inclination to destructive metabolism. It is a general law in the courtship of the sexes that the male seeks the female. The secondary sexual characters of the male are developed with puberty and in some cases these sexual distinctions come and go with the breeding season. What we know as physiological energy is the result of the dissociation of atoms in the organ- ism ; expressions of energy are the accompaniment of the kata- bolic or breaking-up process, and the brighter color of the male, especially at the breeding season, results from the fact that the waste products of the katabolism are deposited as pigments.
When we compare the sexes of mankind morphologically
'"If we take the highly decorated species; that is, animals marked by alternate dark or light bands or spots, such as the zebra, some deer, or the carnivora. \ve find, first, that the region of the spinal column is marked by a dark stripe; secondly, that the regions of the appendages, or limbs, are differently marked ; thirdly, that the flanks are striped or spotted along or between the regions of the lines of the ribs ; fourthly, that the shoulder and hip regions are marked by curved lines ; fifthly, that the pattern changes, and the direction of the lines or spots, at the head, neck, and every joint of the limbs ; and lastly that the tips of the ears, nose, tail, and the feet and the eye are emphasi/cd in color. In spotted animals the greatest k-ncth >f tin- spot is generally in the direction of the largest development <>f the skeleton." A. Tvi.ou, Coloration in Animals and Plants, 1 886, p. Q2.
A. R. WALLACE, Darwinism, chap. 10.
