Wilson — The Multiple Coupling of Mendelian Factors. 373 



Hybrid 

 silver 

 male. 



MM 

 E h 

 S g 



IV. 

 and 



English (pure) 

 silver 

 female. 



should give 



English silver males. 



English English English English 



silver gold silver gold 



females. females. females. females. 



MM 

 E E 



S S 



MM 

 E E 

 S g 



MM 

 R h 



8 8 



Mr. Jones got English silver males and females, and English gold females. 

 He writes that this experiment was carried out by several people, and that 

 taken altogether the proportions were 4:3:1. The proportion of silver 

 to gold females should have been 1 : 1. The discrepancy is likely to be 

 accounted for by some of the females not having been pure for English type. 

 The English silver breed is only about ten years old, and undoubtedly many 

 hens which breeders consider pure are not pure genetically. 



It will be well to bring the foregoing result into line with previous work. 

 Castle and Pearl showed that the American Barred Plymouth Eoeks are 

 merely black fowl having portions of their feathers lacking colour, i.e. barred. 

 The "silver" Campine is therefore a black fowl with colourless bars on its 

 plumage; and the black colour is dominant to the golden. Then, putting 

 Bl for black and Bd for barred, a silver Campine hen of the Belgian breed 

 is faetorially represented by 



M 



b 



Bl 

 Bd 



Note. — It will be noticed that experiments II and IV are apparently the 

 same, but, in the former, the hens, though hybrids, were necessarily pure 

 for E, while, in the latter, the hens were not necessarily pure for E, though 

 " pure bred " from the breeder's standpoint. 



SCIENT. PKOC. K.D.S., VOL. XIV., NO. XXX. 



