SEXUAL SELECTION 101 



ably act. At the same time Weismann points out 

 that secondaiy sexual characters, which at first appear 

 in one sex only, may be transmitted later on through 

 inheritance to both sexes and thus become the essen- 

 tial characters of a new species. Sexual selection 

 would then seem to be a more powerful factor than is 

 commonly believed. 4 



At the present day, however, this Darwinian hy- 

 pothesis is being submitted to harsh criticism and has 

 even been abandoned by many naturalists. We will 

 review briefly the principal objections raised against 

 it by various scientists. 



Some of them attack Darwin's statement as to the 

 numerical predominance of the males, a necessary 

 premise of the theory of sexual selection. As in most 

 species, at least among the vertebrates, males and fe- 

 males exist in about equal numbers, the individuals 

 endowed with attractive characters, the opponents of 

 this theory say, do not reproduce themselves to the 

 exclusion of the others; even if they should be fa- 

 voured at first, the others would always manage to 

 secure a female. Under such conditions it is difficult 

 for a character to become developed and constant, as 

 the number of individuals which possess it cannot be 

 greater in the second than in the first generation. 



We know that Darwin himself did not by any 

 means take an original numerical inequality of the 



* A. Weismann-. The Evolution Theonj, Vol. I, Chapter XL 



