n8 DARWINISM TO-DAY. 



and definitive choice among the males on the part of the 

 female ? And it is this actual choosing which is the neces- 

 sary basis for the theory of sexual selection. 



How explain the well-known cases of a similar extra- 

 development of plumage in the nuptial season by both 

 How explain m ales and females, as in certain herons and 

 ornaments in other birds ? And what of those other cases in 



females or , . , . . r . , . 



common to both which it is the female that is the bnghter-col- 

 sexes? oured individual of the pair? To explain the lat- 



ter case Darwin assumes that in these cases the males have 

 done the selecting, but even this rather too easy reversal of 

 the situation postulated as a fundamental generalisation 

 of the theory does not explain the first of the questions in 

 this paragraph. Do both sexes among the herons do 

 selecting? 



Morgan 7 lists twenty objections to the sexual selection 



theory, several of which are identical with those already 



mentioned in the foregoing paragraphs, but 



Morgan's hst amO ri2f which are several to which we have not 



of objections. 



referred. One of these is that "some of the 

 objections that apply to the theory of natural selection 

 apply also \vith equal force to the theory of sexual selection 

 in so far as the results in both cases are supposed to be the 

 outcome of the selection of individual, or fluctuating, varia- 

 tions. If these variations appear in only a few individuals, 

 their perpetuation is not possible, since they will soon dis- 

 appear through crossing. It would be, of course, preposter- 

 ous to suppose that at any one time only those few indi- 

 viduals pair and leave descendants that have 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 ac- 

 cumulation of a variation in a given direction could not go 

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



