Views of Thomson and Geddes 



male organisms are the result of this male ten- 

 dency to dissipate energy. In the spermatozoon 

 the dissipated energy appears in the form of 

 active movement ; in the adult organism it takes 

 the shape of plumes and other ornaments, of song 

 and contests for the females. 



This theory, however, does not explain what 

 we might call the haphazard nature of sexual 

 dimorphism. If sexual dissimilarity is due to the 

 tendency of the male to dissipate energy, why do 

 we see very marked dimorphism in one species, 

 and no dimorphism in a very nearly allied 

 species? Why are the males larger than the 

 females in some species, and smaller in other 

 species ? Again, how is it that in certain species 

 of birds the quails of the genus Turnix, the 

 Painted Snipe (Rhynckaa), and the Phalaropes 

 it is the female who possesses the more showy 

 plumage ? Moreover, this theory, equally with 

 that of Wallace, does not explain why the ex- 

 crescences which characterise the male appear in 

 various parts of the body in different species. 



STOLZMANN'S THEORY 



Stolzmann has made an ingenious attempt to 

 explain why in birds the cock is so frequently 

 more conspicuously coloured than the hen. He 

 asserts that among birds the males are more 

 numerous than the females, and that this pre- 

 ponderance is not advantageous to the species. 



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