458 INTERNAL SECRETIONS 



versicolor female in the ancestry, the crosses being made 

 thus : 



formosus $ x versicolor ^ 



I 



hybrid $ x versicolor ,^ 



versicolor ? (5) hybrid (? (2) 



The female offspring of the second cross were nevertheless 

 pure versicolor in their secondary sexual characters. Their 

 two brothers still showed considerable traces of their hybrid 

 ancestry. Similar results were obtained by the same investi- 

 gator with crosses between the Swinhoe and Silver Pheasants, 

 in which it was shown that the Swinhoe male transmits the 

 plumage-characters of the Swinhoe female" {Doncaster, 1914, 

 p. 109). The examples could be multiphed. Further, the 

 existence of sex-limited inheritance must be mentioned here. 

 Many cases of this kind are known. One of the best examples 

 is the result first obtained by Pearl and Surface when mating 

 Pl3rmouth Rocks and Cornish Indian Game. The Plymouth 

 Rocks are good winter egg producers, Cornish Game mediocre 

 ones. Females from a cross between Plymouth Rock and 

 Cornish Game always inherit capacity of egg production only 

 from the father, and not from the mother. If we wish to obtain 

 good winter egg producers we must cross male Plymouth 

 Rocks and female Cornish Game, and not vice versa, as one 

 might think at first sight. The Plymouth Rock cock transmits 

 a marked female character {egg production) to female offspring. 

 This fact is also of practical importance ; it is of no use to select 

 for crossing hens with high egg production, as only cocks of the 

 respective strain transmit this special female character. We 

 see, then, that each sex can transmit the sex characters proper 

 to the opposite sex, at least in many cases, and "possibly 

 always," as Doncaster (1914, p. no) says. 



Darwin has made no attempt to give any further explanation 

 of this latency of characters of the opposite sex. His method 

 of thought is really d3mamical or physiological. This is what 

 he says: "In every female all the secondary male characters, 

 and in every male all the secondary female characters, appar- 

 ently exist in a latent state, ready to be evolved under certain 

 conditions." This mode of reasoning is not contrary to the 

 hypothesis of an asexual embryonic soma. Unlike what we 



