101 THE THEORIES OF EVOLUTION 



characters of the male is the vivid coloration of the 

 male during" the breeding period in animal species with 

 external fertilisation. The female fish, for instance, 

 lays her eggs in the water and never even sees the 

 male who is to fertilise them. Cases like this preclude 

 the idea of selection; should they be explained satis- 

 factorily in some other way, the explanation offered 

 would cover the other cases and the theory of sexual 

 selection would have to be abandoned. 



Experiments performed on insects have also sup- 

 plied interesting evidence against it. Mayer and 

 Soule dyed the wings of a male butterfly 

 (Porthetria dispar), and the change in colour did 

 not modify the attitude of the females; on 

 the other hand, the females were aware of the 

 presence or absence of wings and resisted the 

 approach of males whose wings had been cut off. 6 

 Ornamental characters are therefore beyond the 

 sphere of action of sexual selection which seems to be 

 based upon one character, the wings, for which no- 

 body has ever held it responsible. Mayer made an- 

 other, even more conclusive test. He took another 

 species of butterflies (Callosamia promethea) , the 

 male, dark coloured, the female, reddish-brown, cut 

 off their wings and glued on a male the wings of a 

 female and reciprocally. This did not affect in any 



e A. G. Mayer and C. G. Soule: Some Reactions of Caterpillars and 

 Moths. Journal of Experimental Zoology, Vol. Ill, 1903. 



