The Making of Species 



Neo-Lamarckian principles. His theory is set 

 forth in a paper entitled The Heredity of 

 Secondary Sexual Characters in relation to 

 Hormones, which was read before the Zoological 

 Society of London, and published in full in the 

 Archiv fur Entwicklungsmechanik der Organ- 

 ismen. " The significant correlation of male 

 sexual characters," he writes, " is not with any 

 general or essential property of the male sex, 

 such as katabolism (or the tendency to dissipate 

 energy, as we have called it), but with certain 

 habits and functions confined to one sex, but 

 differing in different animals. ... In those 

 animals which possess such (i.e. secondary 

 sexual) characters, the parts of the soma (i.e. the 

 body) affected differ as much as they can differ ; 

 any part of the soma may show a sexual differ- 

 ence : teeth in one mammal, skull in another ; 

 feathers of the tail in one bird, those of the neck 

 in another, and so on. But in all cases such 

 unisexual characters correspond to their functions 

 or use in habits and instincts which are asso- 

 ciated, but only indirectly, with sexual produc- 

 tion. These habits are as diverse and as 

 irregular in their distribution as the characters. 

 The cocks of common fowls and of the Phasi- 

 anidae generally are polygamous, fight with each 

 other for the possession of the females, and take 

 no part in incubation or care of the young, and 

 they differ from the hens in their enlarged 



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