WHAT DETERMINES SEX? 107 



To illustrate contrasted Mendelian char- 

 acters we may select a dozen and place them 

 in parallel columns 



DOMINANT. RECESSIVE. 



Hornlessness in cattle. Presence of horns. 



Short hair in rabbits. Long Angora hair. 



Normal movements in mice. Waltzing in mice. 



Crest in poultry. Absence of crest. 



Broodiness in poultry. Absence of this. 



Unbanded shell in snail. Banded shell. 



Tall stems in peas. Dwarf stems. 



Round seeds in peas. Wrinkled seeds in peas. 



Absence of awn in wheat. Presence of awn. 



Red chaff. White chaff. 



Two-rowed ears in barley. Six-rowed ears. 



Markedly dentate leaves in Slightly dentate leaves, 

 nettles. 



So far, very briefly, the results of experi- 

 ments; but Mendel also suggested an inter- 

 pretation. In the case of the hybrids (FJ 

 he supposed that the germ-cells were formed 

 of two kinds in equal proportions, each kind 

 bearing only one of the two contrasted or 

 alternative characters. If each of the hybrids 

 of the F! generation produces in both sexes 

 50 per cent, of its germ-cells bearing the 

 item or factor corresponding to the dominant 

 character, and 50 per cent, not bearing it, if 

 fertilisation be fortuitous, 25 per cent, of the 



