SEXUAL SELECTION 619 



getically or less persistently than on the males in the last 

 class. Mr, Wallace believes that the males have had their 

 colors rendered less conspicuous for the sake of protection 

 during the period of incubation; but the difference between 

 the sexes in hardly any of the foregoing cases appears sufla- 

 ciently great for this view to be safely accepted. In some 

 of the cases the brighter tints of the female are almost con- 

 fined to the lower surface, and the males, if thus colored, 

 would not have been exposed to danger while sitting on the 

 eggs. It should also be borne in mind that the males are 

 not only in a slight degree less conspicuously colored than 

 the females, but are smaller and weaker. They have, more- 

 over, not only acquired the maternal instinct of incubation, 

 but are less pugnacious and vociferous than the females, and 

 in one instance have simpler vocal organs. Thus an almost 

 complete transposition of the instincts, habits, disposition, 

 color, size, and of some points of structure, has been ef- 

 fected between the two sexes. 



Now if we might assume that the males in the present 

 class have lost some of that ardor which is usual to their 

 sex, so that they no longer search eagerly for the females; 

 or, if we might assume that the females have become much 

 more numerous than the males — and in the case of one In- 

 dian Turnix the females are said to be "much more com- 

 monly met with than the males"" — then it is not improbable 

 that the females would have been led to court the males, in- 

 stead of being courted by them. This, indeed, is the case 

 to a certain extent with some birds, as we have seen with 

 the peahen, wild turkey, and certain kinds of grouse. Tak- 

 ing as our guide the habits of most male birds, the greater 

 size and strength as well as the extraordinary pugnacity of 

 the females of the Turnix and emu, must mean that they en- 

 deavor to drive away rival females, in order to gain posses- 

 sion of the male; and on this view all the facts become clear; 

 for the males would probably be most charmed or excited by 



«» Jerdon, "Birds of India," vol. iii. p. 698 



