THEORY OF EVOLUTION 



47 



black. In other words, the factor for white and 

 the factor for black separate in the germ cells 

 of the hybrid Andalusian birds (fig. 16) . 



Tlie third case is IMendel's classical case 

 of yellow and green peas (fig. 17) . He crossed 

 a plant belonging to a race haying yellow peas 

 with one haying green peas. The hybrid plants 

 had yellow seeds. These liybrids inbred o-aye 

 three yellows to one green. The explanation 



Fig. 17. Diagram of Mendel's cross between yellow (dom- 

 inant) and green (recessive) peas. 



