38 THE AMERICAN JOURNAL OF SOCIOLOGY
even in the larval stage. So considerable is the difference in size between the male and female cocoons of the silk-moth that in France they are separated by a particular mode of weighing. 1 The same superiority of the female is found among fishes and reptiles, and this relation wherever it occurs may be associated with a "habit of life in which food conditions are simple and stimuli mandatory. As we rise in the scale toward backboned and warm-blooded animals the males become larger in size, and this reversal of relation, like the development of offensive and defensive weapons, is due to the superior variational tendency of the male resulting in characters which persist in the species wherever they prove of life-saving advantage. 2
The superior activity and variability of the male among lower forms has been pointed out in great detail by Darwin and con- firmed by others.
Throughout the animal kingdom, when the sexes differ in external appearance, it is, with rare exceptions, the male which has been more modi- fied ; for, generally, the female retains a closer resemblance to the young of her own species, and to other adult members of the same group. The cause of this seems to lie in the males of almost all animals having stronger pas- sions than the females. 3
Darwin explains the greater variability of the males as shown in more brilliant colors, ornamental feathers, scent- pouches, the power of music, spurs, larger canines and claws, horns, antlers, tusks, dewlaps, manes, crests, beards, etc., as due to the operation of sexual selection, meaning by this "the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction" 4 the female choosing to pair with the more attractive male, or the stronger male prevailing in a contest for the female. Wallace 5
X G. DELAUNAX, "De 1'dgalite* et ine'galite' des deux sexes," La Revue scien- tifique, 3 Sept., 1881 ; C. DARWIN, Descent of Man, chap. 10.
9 A. WEISMANX, Essays upon Heredity, Vol. I, "The Duration of Life," has shown that size and longevity are determined by natural selection.
3C. DARWIN, Descent of Man, chap. 8.
4 DARWIN, ibid., chap. 8.
s A. R. WALLACE, Contributions to the Theory of Natural Selection, 1870, chap. 3.
