54 THEORY OF EVOLUTION 



of a different organism. We can explain this 

 result as due to the assortment of factors for 

 these characters in the germ cells according to 

 a definite law. 



As a second illustration let me take the clas- 





'YR 



/Y 

 YR 



YW 

 YR 



Y R 



YR 



YR GW 



YW 

 YW 



GR 

 GR 



Y R 



YR 

 GR 



YW 

 GR 



GR 





GW 



GW. 



YR 



FIG. 22. Diagram to show the history of the factor pairs 

 yellow-green and round-wrinkled of the cross in Fig. 21. 



