2 28 Habit and Instinct. 



the traditional process. Any individual which, through 

 lack of vigour or other more positive defect, was excluded 

 from, or exhausted by, the dance or other performance, 

 would so far drop out of the social life and run less chance 

 of taking his share in the special business of pairing, 

 not in virtue of any preferential mating, but just because, 

 while others were stimulated by the performance to sexual 

 activity, the weaklings were exhausted and excluded from 

 the full life of the community. Song-birds matched against 

 each other have been known to sing till they dropped 

 exhausted to death. The extravagant and prolonged 

 antics and dances may well be a means of eliminating the 

 weakly and leaving the strongest and toughest dancers in 

 full sexual vigour to perpetuate, not only their strength and 

 toughness, but also any congenital tendency they may 

 possess towards the specialized performance of the definite 

 activity. The period of dancing and display is also a 

 period of pugnacity, and those whose vital power is lowered 

 by the strain of the one will be those who are worsted in 

 the combats arising out of the other. So that out of the 

 traditional dance there may arise a process of natural 

 selection, whereby the most vigorous males, those with the 

 greatest amount of reserve power for the development of 

 plumage and for effective mating, and with the greatest 

 congenital tendency to follow the traditions of the com- 

 munity, would survive to transmit their vigour as dis- 

 played in certain definite ways. 



And if we may admit, on the part of the females, 

 whether they participate in the dance or not, a heightening 

 of the sexual emotion at the period of predominant activity, 

 we may further suppose that there is at least this much 

 of preferential mating as well — that the hens accept most 

 readily the attentions of those through whose antics this 

 heightened sexual impulse has been aroused. 



