2i8 Habit and Instinct. 



the existence of an aesthetic standard in this case than 

 there is to hypothecate a gustatory ideal in the case 

 of the chick that eats a juicy worm. Stripped of all its 

 unnecessary aesthetic surplusage, the hypothesis of sexual 

 selection suggests that the accepted mate is the one that 

 most strongly evokes the pairing instinct. 



That the sexual impulse, and certain specialized 

 activities which are associated with it, is instinctive, 

 and truly congenital though deferred, stands in no need 

 of demonstration. It affords, however, a good illustration 

 of that co-operation between internal organic factors and 

 an external exciting cause which is characteristic probably 

 of all, and certainly of the most highly developed, instincts. 

 We have seen that, in other matters, congenital instinctive 

 tendency affords an unspecialized basis on which are 

 founded habits in the formation of which individual choice 

 has likewise played its part. It is difficult to accept the 

 view that individual choice has played no part where the 

 sexual instincts are concerned. But supposing that it 

 has played its part — and this is essential to the con- 

 tention of those who accept sexual selection — the effects 

 will be wrought into the congenital tissue of the race if, 

 and only if, there are certain individuals which, through 

 failure to elicit the pairing response, die unmated. Is 

 preferential mating, supposing it to occur, carried to such 

 a degree that some individuals fail to secure a mate? 

 That is the question. If so, sexual selection is a factor 

 in race-progress ; if not, though it may occur in nature, 

 it is inoperative as a means of evolutionary development. 

 The whole question, in itself a difficult one, is further 

 complicated by the fact that the males which are pos- 

 sessed of the most exuberant vitality, and are therefore 

 by hypothesis rendered the most acceptable through 

 emotional suggestion, are likely to compete with other 



