244 T - H ' MORGAN. 



as completely so as the Sebright. Still there is no overlapping 

 with the cock-feathered type. The F 2 and the back-cross cocks 

 are either hen-feathered or cock-feathered ; the former showing 

 about the same range of variability as the F x cocks. The failure 

 of perfect dominance in some of the F x and F 2 cocks may indi- 

 cate that the heterozygote has a wider range (the gene not com- 

 pletely dominant), or that subsidiary genes introduced from the 

 cock-feathered birds allow a wider range of variability of the 

 character. Only an extended series of experiments can settle 

 this point. 



In the Campines also there is evidence that the gene for hen- 

 feathering is inherited and dominant. In a paper published sev- 

 eral years ago (1914) by the Rev. E. L. Jones, crosses between 

 two races of Campines are described, one of them belonging to 

 a race (Belgium) in which hen-feathered birds are the recog- 

 nized standard, the other (English) belonging to a race in which 

 cock-feathering is the standard. The evidence seems to show 

 that hen-feathering is dominant, also that there is segregation in 

 the back-cross, and in F 2 as in the Sebrights. There are however 

 serious inconsistencies in some of the results that may be ac- 

 counted for on the assumption that the hens of the cock-feathered 

 race were not pure for the character-pair in question ; an as- 

 sumption that does not seem too improbable, when one recalls 

 that the latter, the dominant type, has often been mixed with 

 cock-feathered strains. Whether the gene for hen-feathering 

 is the same as that in the Sebrights can, of course, only be de- 

 termined by crossing the two breeds. From what I have heard it 

 appears that in this country the Campines, even, when said to be 

 pure for hen-feathering, are not so " fixed " as are the Sebrights ; 

 for, the latter do not " break " as do the Campines unless cas- 

 trated, while the Campines are reported to show quite often a 

 few or many cock-feathers. It is recognized that when sick or in 

 poor condition such feathers appear and may be replaced later 

 by hen-feathers if the bird recovers. I have some feathers from 

 an old bird of another strain, purporting to be pure for hen- 

 feathering, that show unmistakable changes in the direction of 

 cock-feathers (Fig. 10). At the time the bird had been confined 

 and was in poor condition. This difference in the two races 



