BIRDS 83 



ponderance of males in Nature ; even man is no 

 exception to the rule, because there are more boys 

 born than girls every year. If the females are in 

 the majority in later life, that is because the males 

 are at all periods of life exposed to a higher mortality. 1 



Which males, then, are selected ? 



According to Darwin, there is a double struggle 

 for the opportunity to reproduce. In the first the 

 males fight actively for the possession of the females ; 

 the stronger drive away the weaker, the better armed 

 conquer the weaponless. In this way, for instance, 

 the cock's spurs and the stag's antlers would be 

 explained by selection. In the second form of selection 

 the males are chosen by the females. These are 

 supposed not to listen to every suitor, but to choose 

 the one that pleases them most. Thus the bullfinches, 

 for instance, may once have been the same colour 

 in both sexes. Then variations occurred in the males, 

 which showed a shade of red in the breast. This 

 pleased the females, and the continuous selection of 

 the redder ones led to the endowment of the male 

 bullfinches with the bright red breast they now have. 



The first kind of sexual selection is based on well- 

 known facts, and has never been seriously called 

 into question from the Darwinian side ; it is really 

 a special case of natural selection. But the second 

 category has a number of opponents, among whom 

 we find the distinguished naturalist, Dr. A. R. Wallace. 



1 In later years the unhealthy life led by men is to blame for this, 

 monotonous labour without regard to the body, and the use of alcohol 

 and tobacco. 



