DAKWIN AND SEXUAL SELECTION 141 



as an interpretation of many appearances usually 

 explained by Natural Selection. Hence Sexual 

 Selection, incidentally discussed in other sections 

 of the present essay, need not be considered at 

 any length, in the section specially allotted to it. 

 Although so interested in the subject and not- 

 withstanding his conviction that the hypothesis 

 was sound, Darwin was quite aware that it was 

 probably the most vulnerable part of the Origin. 

 Thus he wrote to H. W. Bates, April 4, 1861 : 



'If I had to cut up myself in a review I would have 

 [worried ?] and quizzed sexual selection ; therefore, though 

 I am fully convinced that it is largely true, you may imagine 

 how pleased I am at what you say on your belief.' l 



The existence of sound-producing organs in 

 the males of insects was, Darwin considered, 

 the strongest evidence in favour of the operation 

 of Sexual Selection in this group. 2 Such a con- 

 clusion has received strong support in recent 

 years by the numerous careful observations of 

 Dr. F. A. Dixey 3 and Dr. G. B. Longstaff 4 on 

 the scents of male butterflies. The experience 

 of these naturalists abundantly confirms and ex- 

 tends the account given by Fritz Muller 5 of the 

 scents of certain Brazilian butterflies. It is a 

 remarkable fact that the apparently epigamic 

 scents of male butterflies should be pleasing to 



1 More Letters', i. 183. 2 Life and Letters, iii. 94, 138. 



3 Proc. Ent. Soc. Lond., 1904, Ivi. ; 1905, xxxvii., liv. ; 1906, ii. 



4 Proc. Ent. Soc. Lond., 1905, xxxv. ; Trans. Ent. Soc. Lond., 1905, 

 136 ; 1908, 607. 



5 Jen. Zeit., xi., 1877, 99; Trans. Ent. Soc. Lond., 1878, 211. 



