SEX-CHARACTERS IN EVOLUTION 129 



There is a tendency among Mendelians and 

 mutationists to overestimate the importance of 

 experiments in comparison with reasoning, either 

 inductive or deductive. Bateson, however, has 

 admitted that Mendelian experiments and observa- 

 tions on mutation have not solved the problem of 

 adaptation. It seems to be demanded, nevertheless, 

 that characters must be produced experimentally 

 and then inherited before the hereditary influence 

 of external stimuli can be accepted. Kammerer's 

 experiments in this direction have been sceptically 

 criticised, and it must be granted that the evidence 

 he has published is not sufficient to produce complete 

 conviction. But experiments of this kind are from 

 the nature of the case difficult if not impossible. 

 There is, however, another method namely, to take 

 a character which is certainly to some extent heredi- 

 tary, and then to ascertain by experiment if it is 

 ' acquired.' If it be proved that a hereditary 

 character was originally somatogenic, it follows that 

 somatogenic characters in time become hereditary. 

 This is the reasoning I have used in reference to my 

 experiments on the production of pigment on the 

 lower sides of Flat-fishes, and I obtained similar 

 evidence with regard to the excessive growth of the 

 tail feathers in the Japanese Tosa-fowls, 1 which is a 

 modification of a secondary sexual character. In 

 these fowls the feathers of the tail in the hens are only 

 slightly lengthened. 



I learned from Mr. John Sparks, who himself 

 brought specimens of the breed from Japan, that the 

 Japanese not only keep the birds separately on high 



1 'Observations and Experiments on Japanese Long-tailed Fowls,' 

 Proc. Zool. Soc., 1903. 



I 



