214 Evolution and Adaptation 



a few individuals, their perpetuation is not possible, since 

 they will soon disappear through crossing. It would be, of 

 course, preposterous to suppose that at any one time only 

 those few individuals pair and leave descendants that have the 

 secondary sexual characters developed to the highest point, 

 but if something of this sort does not occur, the extreme of 

 fluctuating variations cannot be maintained. Even if half 

 of the individuals are selected in each generation, the accu- 

 mulation of a variation in a given direction could not go 

 very far. The assumption, however, that only half of all the 

 individuals that reach maturity breed, and that all of these 

 are chosen on account of the special development of their 

 secondary sexual characters, seems preposterous. Further- 

 more, if it is assumed that the high development of the new 

 character appears in a large number of individuals, then it 

 is not improbable that its continued appearance might be 

 accounted for without bringing in, at all, the hypothesis of 

 sexual selection. 



2. But even supposing that the females select the most beau- 

 tiful males, then, since in the vast majority of higher animals 

 the males and the females are in equal numbers, the others will 

 also be able to unite with each other in pairs after this first 

 selection has taken place. Nothing will therefore be gained 

 in the next generation. It is interesting to see how Darwin 

 attempts to meet this argument. He tries to show in the 

 case of birds, that there are always unpaired individuals, but 

 since the few facts that he has been able to collect show that 

 there are as many additional females as males, the argument 

 proves too much. A few species are polygamous, one male 

 having a number of female birds ; but on this basis we can 

 only account, at best, for the development through com- 

 petition of the organs of offence and defence used to keep 

 away the weaker males. Yet it is just amongst these birds 

 that we often find the ornamental characters well developed. 

 In fact, since all the females in such cases are selected, and 



