16 



THE GENETIC AND THE OPERATIVE EVIDENCE 



feathered birds. The numbers are too small to be significant, taken by 

 themselves. The expectation for 2 dominants, both essential to hen- 

 feathering, is 1 to 3, and this is in agreement with 2 to 7 as found. 

 It seems, then, more probable from the evidence of the F 2 and of the 

 back-cross combined that there are two dominant factors present in 

 the Sebright that make the male hen-feathered, and since the race 

 breeds true to hen-feathering, both factors must be present in homo- 

 zygous condition unless an undetected lethal destroys some of the 

 classes. 1 



Gold Male 



(Belgian imported 

 from Brussels.) 



X Silver Female 

 (Product of English 

 type males for 7 

 generations in my 

 own yards ) 



I 

 6 Silver Males 

 (Belgian type) 



6 Gold Females 



B 



Silver Cross-Bred X Gold Cross-Bred 



Male 

 (offspring of A) 



Female 

 (offspring of A) 



4 Silver 2 Gold 



Males Males 



(Belgian (Belgian 



type) type) 



2 Silver 

 Females 



5 Gold 

 Females 



Silver Male 



X Gold Female 



6 Silver Males 

 (English type) 



6 Silver Females 



D 



Silver Cross-Bred X Silver Cross-Bred 



Male 

 (Offspring of C) 



Female 

 (Offspring of C) 



Silver Males Silver Females Gold Females 

 (English type) 



E 



Silver Male (offspring of C) 



Gold Female (pure) 



Silver Males Silver Males Gold Males Gold Males Silver Females Gold Females 

 (Eng. type) (Belgian type) (Eng. Type 1912) (Belgian type) 



F 



Silver Male (offspring of C) 



X 



Silver Female (pure) 



Silver Males (English type) 



Silver Females 



Gold Females 



Smith and Haig have reported the following curious case of hen- 

 feathering. Smith had a breed of White Leghorns with cocks of two 

 classes — those that assumed cock plumage at 6 months and those 

 that are like the hens for 8 months, after which they slowly assumed 

 the cock-feathering. The difference is hereditary and appears to 

 segregate. Possibly this breed had one factor at least for hen-feathering 

 that is effective for young birds, but not for older ones, or some of the 



1 The expectation for 1 dominant and 1 recessive factor is so nearly the same as for 1 dominant 

 alone that for the numbers obtained no difference between the two cases could be detected. 



