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. It 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 toa 
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. Witha 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 
