756 The American Naturalist. [August, 
male and female, (2). The same anthithesis is seen when we contrast, 
as we shall afterwards do in detail, the actively’ motile, minute male 
element of most animals and many plants with the larger, passively 
quiescent female cell or ovum. ' 
“ While it is easy to point to the general physiological import of large 
size and the reverse, physiology is not yet far enough advanced to afford 
firm foot-hold in dealing with the details of secondary sexual char- 
acters. It is only possible to point out the path which will eventually . 
lead us to their complete rationale. This path will appear less vague 
if reverted to after some of the succeeding chapters have been grasped. 
The point of view is simple enough. The agility of males is not a 
special adaptation to enable that sex to exercise its functions with 
relation to the other, but is a natural characteristic of the constitutional 
activity of maleness; and the small size of many male fishes is not an 
advantage at all, but simply again the result of the contrast between the 
more vegetative growth of the female, and the costly activity of the 
male. So, brilliancy of color, exuberance of hair and feathers, activity 
of scent-glands, and even the development of weapons, are not, and 
cannot be (except teleologically), explained by natural selection, but 
in origin and continued development are outcrops of a male as 
opposed to a female constitution. To sum up the position in a para- 
dox, all secondary sexual characters are at bottom primary, and are 
expressions of the same general habit of body (or to use a medical 
term, diathesis), as that which results in the production of male ele- 
ments in the one case, or female elements in the other, 
“< Three well-known facts must be recalled to the reader's mind at this 
point; and firstly, that in a great number of cases the secondary 
sexual characters make their appearance step by step with sexual 
maturity itself. When the animal, be it bird or insect, becomes em- 
phatically masculine, then it is that these minor out-crops are ex- 
hibited. Thus the male bird of paradise, eventually so resplendent, is 
usually in its youth comparatively dull and female-like in its coloring 
and plumage. Very often, too, whether in the wedding-robes of male 
fishes or in the scent-glands of mammals, the character rises and wanes 
in the same rhythm as that of the reproductive periods. It is impossi- 
ble not to regard at least many of the 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 characters tend to remain 
undeveloped. Thus, as Darwin notes, stags never renew their antlers 
after castration, though normally of course they renew them each 
