68 



INHERITANCE IN POULTRY. 



hybrids bred inter se, the offspring exhibits one or the other of the parental 

 conditions each in 25 per cent of the cases and the heterozygous condition 

 in 50 per cent. To decide between these rival hypotheses we have to appeal 

 to the statistics of occurrence of the different forms of comb. All cases 

 (Series I and II) are combined in the following table, showing distribution 

 in the second hybrid generation : 



The foregoing table reveals several things. First, the actual distribution 

 of comb form in the second generation accords better with the hypothesis of 

 particulate inheritance than that of dominance of both single and lateral 

 comb. That there is an excess of single comb and deficiency of Y comb is 

 partly accounted for by occasionally counting a potentially Y comb but 

 actually single (or nearly single) comb as a true single. Secondly, the 

 hypothesis of dominance demands the occurrence of a fourth form — pre- 

 sumably no comb — in (3% per cent of the cases. No combless fowl was 

 raised to maturity, and the only possible cases were seen in still very young 

 or unhatched chicks. Probably no true combless bird appeared. From 

 both of these considerations I conclude, provisionally, in favor of the theory 

 that the Y comb is reproduced from the median and the lateral by particulate 

 inheritance. 



NOSTRIL FORM. 



The sum of results in Series I, II, and III (narrow x high nostril) gives : 



A close agreement exists between the percentage obtained in each genera- 

 tion and the expectation on the Mendelian theory, assuming that natiow 

 nostril is dominant. The statistics do not, however, tell the whole story. 

 In 36 per cent of the cases in the Fj generation the nostril was wider than in 



