The Making of Species 
Neo-Lamarckian principles. His theory is set 
forth in a paper entitled Zhe Heredity of 
Secondary Sexual Characters in relation to 
Hormones, which was read before the Zoological 
Society of London, and published in full in the 
Archi fiir Entwicklungsmechantk der Organ- 
wsmen. “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 (ze secondary 
sexual) characters, the parts of the soma (ze. 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- 
anide 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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