Constitution of the White Leghorn Breed. 161 



Employing these symbols, the zygotic formula of the Burred 

 Plymouth Rock cT becomes 



BBff, 



foniiing gametes 



Bf'Bf 



The zygotic formula of the 9 becomes 



BbFf, 

 fonning gam.etes 



Bf • bF 



since, by hj-pothesis, B and F (or their complementary combination, 

 bf), cannot be present in the same gamete. 



The matings occurring in the propagation of pure Barred Ply- 

 mouth Rock stock would therefore be represented: 



cf' Bf ■ Bf X 

 9 Bf • bF = 

 9 9 BbFf, Barred 

 cf cf BBff, Barred 

 the 99 being heterozygous for barring and the cf cf homozygous. 

 If, however, we have the mating between the Barred Plymouth 

 Rock and some dark non-barred brecxl, such as the Rhode Island Red, 

 the case is different, and the results vary accordingly as the cf is 

 chosen from one breed or the other. 



The zygotic formula of the R. I. Red cT (non-barreil) would be 



66//, 



forming gametes: 



bf • hf 



while the formula of the Barred Rock 9 is as showTi above. This 

 mating would therefore become: 



cf 6/ • 6/ X 



9 bF • Bf = 



& & Bbff, Barred 

 99 66F/, Black 



