84 CONTROLLED NATURAL SELECTION 



The occurrence of only a single variation is 

 necessary for this conception. Because females 

 who happen to choose the most conspicuous 

 males, will be more liable to escape destruc- 

 tion than females who happen to be mated 

 with less conspicuous males : and the former 

 females will therefore be more likely to hand 

 on this male character than the latter females. 

 This applies to all the purposely conspicuous 

 characters of males. 



Stolzmann in 1885 put forward a theory to 

 account for the secondary sexual characters 

 of birds, which in some respects resembles 

 this theory. 



Having observed that males are often more 

 numerous than females, he justly concluded 

 that the species' food supply was being wasted 

 on them and that this excess of males was 

 harmful to the species ; more especially be- 

 cause he believed that the paired females 

 during the breeding season were harried by 

 celibate males, with injurious results. He 

 therefore conceived that the brilliant colours 

 of the males arose in order that they might 

 easily be seen by enemies and their ranks 

 thus thinned. 



This theory was very short-lived, because 

 it was speedily pointed out, that if males 



