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) . 



The third case is Mendel's classical case 

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

 a plant belonging to a race having yellow peas 

 with one having green peas. The hybrid plants 

 had yellow seeds. These hybrids inbred gave 

 three yellows to one green. The explanation 



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

 inant) and green (recessive) peas. 



