vi Preface to the Second Edition. 



structure ; nor must we forget what I have called " correlated " 

 growth, meaning, thereby, that various parts oi the organisation 

 are in some unknown manner so connected, that when one part 

 varies, so do others; and if variations in the one are accu- 

 mulated by selection, other parts will be modified. Again, it 

 iias been said by several critics, that when I found that many 

 details of structure in man could not be explained through 

 natural selection, I invented sexual selection ; I gave, however, 

 a tolerably clear sketch of this principle in the first edition oi 

 the ' Origin of Species/ and I there stated that it was applicable 

 to man. This subject of sexual selection has been treated at 

 full length in the present work, simply because an opportunity was 

 here first afforded me. I have been struck with the likeness of 

 many of the half-favourable criticisms on sexual selection, with 

 those which appeared at first on natural selection; such as, 

 that it would explain some few details, but certainly was not 

 applicable to the extent to which I have employed it. My 

 conviction of the power of sexual selection remains unshaken ; 

 but it is probable, or almost certain, that several of my con- 

 clusions will hereafter be found erroneous ; this can hardly fail 

 to be the case in the first treatment of a subject. When 

 naturalists have become familiar with the idea of sexual selection 



* 



it will, as I believe, be much more largely accepted; and it 

 has already been fully and favourably received by several capable 

 judges. 



Down, Beckenham, Kent, 

 September 1871. 



