90 INHERITANCE IN POULTRY. 



breed has been discussed by Bateson and Punnett (1905, p. 126), and they 

 find, what is the universal testimony of breeders, that (as stated also at page 

 76) the blues bred inter se produce some white and some blacks, but still 

 more blues. Until more complete statistics have been gained on the pro- 

 portions of colors in the offspring, the interpretation of blue must remain 

 uncertain. 



Hybrid forms are, then, frequently cases of particulate inheritance in 

 which the hybrid gametes are not mosaic ; consequently whenever ' ' pure ' ' 

 offspring are produced, as in Fj, these reassume the character of the pure 

 race. In some cases, as in the cuckoo Dorking and the Dominique (from 

 which our barred Plymouth Rock has been derived), the heterozygous form 

 of barred plumage has become fixed, so that only barred offspring are pro- 

 duced. A mosaic gamete has been created. The blue coloration has never 

 yet been fixed as a permanent hybrid form. The method of fixing a hybrid 

 form is urgently in need of investigation. 



REVERSION. 



This term has been used rather loosely in the past for the appearance in 

 hybrids of characteristics not visible in the immediate parents of the hybrids 

 and often belonging to remote ancestors. Darwin (1876) made much use 

 of this term in describing his results. He believed that the occurrence of 

 " reversion " gave a useful key to ancestry. It is worth while to consider 

 his observations and experiments. He mentions the fact that ' ' purely bred 

 Game, Malay, Cochin, Dorking, Bantam, and Silk fowls may fre- 

 quently or occasionally be met with, which are almost identical in plumage 

 with the wild G. bankiva. ' ' But does this indicate anything else than that 

 this type of coloration has persisted in certain primitive races, like the Game, 

 and has been transplanted from them to the new races ? Darwin crossed a 

 black Spanish cock with various white and white- and-black hens of pure 

 breed. The offspring of this cock crossed with a silver- spangled Polish hen 

 and with a white Cochin hen showed no sign of reversion to the red color of 

 G. bankiva. The male offspring of a spangled or silver Hamburgh hen 

 showed white in the hackles and a reddish yellow on the saddle. Darwin 

 regarded this as a " first sympton of reversion ; ' ' but in the first of these 

 peculiarities the hybrid resembles G. bankiva less than the Dark Brahma. 

 The offspring of a white Game hen with the Spanish cock was at first snow 

 white, but eventually produced the "pile" coloration. Darwin regards 

 this as a partial reversion to G. bankiva ; but it is equally possible that the 

 reversion is only to a pile coloration that is latent in the white from an earlier 

 cross and is brought out when the white is crossed with a dark color. But 

 Darwin's most remarkable hybrid was the offspring of a white Silky hen. 

 Of two cockerels one was black (with light laced hackles) ; the other resem- 

 bled closely a Jungle cock. Darwin admits that the case is extraordinary,. 



