SEXUAL SELECTION 167 



not very far from correct ; the brilliancy of the males is in pro- 

 portion to the excess of the supply. But in many species it is 

 quite possible that the numbers of the sexes are equal, and these 

 the formula does not take into consideration. 



I have now shown, or tried to show, that Sexual Selection, Recapitul- 

 when its working is rightly understood, will account satisfactorily atlon 

 for the secondary sexual characters, even the most extravagant. 

 No other theory attempts to explain the steady accumulation, 

 generation after generation, of each advance in brilliancy. Such 

 an exceptional case as that of Rhyncaea, the Indian Painted 

 Snipe, where the hen is far more showy than the cock, presents 

 no difficulty, if in this genus there is a preponderance of 

 hen birds. This would naturally lead to fights among them, 

 such as do actually occur, and competition for the males. Even 

 if the numbers are equal, yet the system will lead to the best 

 pairing with the best. In any case the species profits by a 

 system which puts a premium upon vigour. 



Not only are secondary sexual characteristics accounted for by 

 Darwin's theory, but the supremacy of Natural Selection is not 

 interfered with. Individuals may be sacrificed, but the species 

 is the gainer. Where polygamy exists the system works most 

 freely, and there its services to evolution must obviously be 

 great ; it must lead to an increase of vigour since in each genera- 

 tion, only the very pick of the males, leave any progeny behind 

 them. 1 



I must now pass on to the consideration of Dr Russel Wallace's Dr Russel 

 theory that male ornamentation is the "natural product and direct Wa ace 

 outcome of superabundant health and vigour." 2 The males in 

 some species are, he maintains, so vigorous that they are exempted 

 from the operation of Natural Selection. It is very strange that 

 Natural Selection should be thus attacked by one of the two great 

 originators of the theory, and that the Darwinian hypothesis should 



1 Among hive-bees only one out of hundreds of drones mates, since there is only 

 one queen. But the mating always takes place on the wing during the nuptial 

 flight, and it is quite possible that by this system one of the most vigorous drones 

 is selected. 



2 Darwinism, p. 295. A similar view is held by Geddes and Thomson, see The 

 Evolution of Sex. 



