420 THE ZOOLOGIST. 



NOTE ON THE ORIGIN OF SEXUAL DIMORPHISM, 

 AND OF NUPTIAL WEAPONS AND ORNAMENT- 

 ATION. 



By G. E. H. Barrett-Hamilton. 



Not long ago* I suggested, from a consideration of the 

 spawning habits of the various species of Oncorhynchus, that 

 secondary sexual characters, as well as the seasonal assumption 

 of nuptial ornaments and weapons, might have had their origin 

 in pathological conditions : that the whole metabolism of the 

 animal is upset in the effort to produce the sexual products, 

 with a result that pigment and matter are set loose in the body, 

 and find their way to new regions, often with a fatal — always 

 with a serious — influence on the animal, but resulting in the 

 production of nuptial adornments and weapons. Mr. Cunning- 

 ham, in parts of his argument,! comes very near this hypothesis — 

 for instance, when he lays great stress on the influence of the 

 veins as a controlling factor in the evolution of sexual charac- 

 ters. Nevertheless, he is most unfortunate to have missed the 

 Reports of Investigations on the Life-History of Salmon, pub- 

 lished by the Fishery Board of Scotland. In these papers both 

 his and my views are supported, and it is clearly shown that in 

 the breeding Salmon, whether male or female, such transference 

 of pigment and matter, both of fats, proteids, phosphorus com- 

 pounds, and iron, actually does take place. 



There remains yet another point upon which I wish to touch. 

 Many naturalists base their arguments on the absence of proof 

 that acquired characters are or can be inherited. Here they 

 have a strong position ; but, considering the matter closely, do 

 we find that secondary sexual characters are in all cases inherited ? 

 The form and detail of an animal's body exist as the expression 

 of, or owe their structure to, two forces, the one purely vegeta- 

 tive, or due to purely nutritive causes, the other sexual. 



- Cf. • Proc. Camb. Phil. Soc' vol. x. pt. v. pp. 279-285. 

 f " Sexual Dimorphism in the Animal Kingdom." 



