PAIRS OF CHARACTERS 133 



an exhaustive inquiry into the causes determining 

 the nature of these two characters — normality and 

 fasciation — has been carried out it is absurd to attempt 

 to interpret them by means of any theory whatsoever. 

 With regard to tallness and dwarfness, a start has 

 been made by ]\Ir. Keeble, who has shown that tallness 

 depends on two characters, length and (rather 

 curiously) thickness of internode ; dwarfness depends 

 on the absence of both of these qualities. Peas 

 which possess only one of them fall into the category 

 known as half-dwarf. 



Before we leave Mendel's seven characters it will 

 be well to pay some attention to a question which 

 can be most conveniently discussed here, though it 

 may seem that none of the questions so far dealt 

 with in this chapter are worth discussing until it 

 has been answered — and in the affirmative, too. The 

 question is, Is there such a thing as dominance ? 

 Does one character hold the stage in the first hybrid 

 generation to the complete exclusion of its partner ? 

 If an affirmative answer cannot be given to these 

 questions, what reason is there in discussing the 

 causes determining dominance, a thing whose reality 

 has not yet been established ? But in the present 

 case it is desirable to present a consistent scheme 

 of the whole set of phenomena, and then to consider 

 to what extent it is justified. Let us take the first 

 pair of characters, cotyledon shape. If we content 

 ourselves, as the impressionist does, with the mere 

 impression produced on the imaided eye, the answer 

 to the question in regard to the existence of dominance 



