io8 BREEDING 



second hybrid generation, of two entirely new 

 characters — the " rose " and " pea " combs — which 

 were not present in either of the parents or in the 

 first hybrid would have been unintelligible to the 

 experimenter who was not familiar with the 9:3:3:1 

 ratio, and with the proof, which this ratio affords, 

 that we are dealing with a cross between two 

 forms which differ in respect of two pairs of 

 characters. 



The reader will have noticed that a new con- 

 ception of the nature of the Mendelian pair of 

 characters has been invoked to explain the pheno- 

 mena of inheritance presented by the characters 

 of the fowl's comb. Mendel's own results led 

 to the conclusion that characters which were 

 inherited in Mendelian fashion were associated 

 together in pairs, such that one member of a pair 

 was dominant and the other recessive. No indica- 

 tion was given of any features which were peculiar 

 to dominant characters — that is to say, no clue 

 was given by which a dominant character could 

 be known or suspected to be dominant before 

 the result of mating it with a recessive one was 

 known. The two members of a pair possessed this 

 feature in common, that they were not merely drawn 

 at haphazard from the characters of the plant, but 

 both pertained to the same part of the organisa- 

 tion of the plant. Thus, yellow and wrinkled do 

 not constitute a pair, but yellow and green. The two 

 members of a pair only differ from one another by 



