Summary and General Conclusions 457 



held firmly to the belief that the individual differences, or 

 fluctuating variations, furnish the material for selection. 

 In this way it could never happen that two competing 

 species could exterminate each other, because in the one 

 the males were better adorned, or killed each other off on 

 a larger scale, owing to the presence of special weapons of 

 warfare. If is clear that on the law of the survival of 

 species, secondary sexual characters cannot be supposed to 

 have evolved because of their value. Their origin is totally 

 inexplicable on this view. In fact, the presence of the 

 ornaments must be in some cases injurious to the existence 

 of the species. The interpretation of this means, I think, 

 that individual competition cannot be as severe as Darwin 

 believed, and cannot lead to the results that he imagined 

 it does. For this reason it seemed important to make as 

 careful an examination of the claims of the theory of sexual 

 selection as possible, and I hope that the outcome of the 

 examination has shown quite definitely that the theory is 

 incompetent to account for the facts that it claims to explain. 

 It is certain in this case that we are dealing with a phe- 

 nomenon that must be studied quite apart from any selective 

 value that the secondary sexual organs may have. If this is 

 granted, it will be seen that there is here a wide field for 

 experimental investigation that is practically untouched. 



It is evident that the first step that will clear the way to a 

 fuller understanding of the problem of evolution must be a 

 more thorough examination of the question of variation. 

 Darwin himself fully appreciated this fact, yet until within 

 the last fifteen years the study of variation has been largely 

 neglected. With a fuller knowledge of the nature of fluctuat- 

 ing variation as the outcome of the studies of Galton, Pear- 

 son, De Vries, and others, and with a fuller knowledge of the 

 possibilities of discontinuous variation as emphasized by 

 Bateson and by De Vries, and, further, with a better knowl- 

 edge of some of the laws of inheritance in these cases, we 



