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 F2 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.^ 



Gold Male 



(Belgian imported 

 from Brussels.) 



X Silver Female 

 (Product of English 

 type males for 7 

 generations in my 

 own yards ) 



6 Silver Males 

 (Belgian type) 



6 Gold Females 



Silver Male X Gold Female 



6 Silver Males 

 (English type) 



6 Silver Females 



Silver Cross-Bhed X Gold Cross-Bhed 



Male Female 



(offspring of A) (offspring of A) 



Silver Cross-Brbd X Silver Cross-Bhed 



Male 

 (Offspring of C) 



Female 

 (Offspring of C) 



I 

 4 Silver 



Males 

 (Belgian 



type) 



I 

 2 Gold 



Males 

 (Belgian 



type) 



2 SUver 

 Females 



I 

 5 Gold 

 Females 



Silver Males Silver Females Gold Females 

 (English type) 



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) 



Silver Male (offspring of C) 



X 



Silver Female (pure) 



I 

 Silver Males (English type) 



I 

 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 bu-ds, but not for older ones, or some of the 



' 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. 



