INHERITANCE OF SEX 253 



His theory involves five distinct assumptions, which 

 will not be gone into here because a much simpler 

 explanation, suggested by Mr. Bateson and now 

 accepted by Mr. Doncaster, has obtained general 

 credence. Mr. Bateson's theory involves two assump- 

 tions, which are as follows, in his own words : — ' 



1. " That the female is heterozygous in sex, 

 femaleness being dominant, and the male a homo- 

 zygous recessive (see pp. 251-2). 



2. " That when in Fl the two dominant characters 

 femaleness and the grossulariata factor co-exist, there 

 is spurious allelomorphism or repulsion between 

 them, such that each gamete takes one or other of 

 these factors, not both."* 



A word in explanation of spurious allelomorphism. 

 True allelomorphism expresses the relation between 

 the dominant and recessive members of the same 

 pair — ^yellow with green, or round with wrinkled. 

 Spurious allelomorphism is a relation between factors 

 belonging to distinct pairs which gives the appearance 

 of their belonging to the same pair. If a relation 

 of this kind, similar to that which exists between the 

 two dominant characters, femaleness and the gros- 

 sulariata character, were to exist between the two 

 dominant characters, yellow and round, in the hetero- 

 zygote produced by crossing a yellow wrinkled with 

 a green round, yellow would repel round, so that they 

 could not both exist in the same gamete, just as in 

 true allelomorphism yellow and green cannot exist 

 in the same gamete ; yellow could only exist in the 



* " Mendel's Principles of Heredity," p. 175. 



