SECONDARY SEXUAL DIFFERENCES 203 



seem to me to render the theory worthless. One con- 

 clusion, however, seems to be justified, and that is 

 that most of them could not have been evolved by 

 natural selection. 



As to sexual selection and the law of combat, I 

 think that they are entirely inadequate to account for 

 the wide range of differences between the sexes. 



Back of all secondary sexual differences are the 

 primary sexual differences, in explanation of which 

 evolution has offered no sufficient theory, and until 

 this is done her work will be incomplete. 



With this very brief and inadequate reference to a 

 few of the difficulties involved in sexual selection, I 

 leave the subject. 



