284 



THE THEORY OF THE GENE 



breeding each individual has become homozygous. This 

 means that the two members of each pair of genes are 

 identical. Hence such material is suitable to carry out 



^vvv* 



r\n 



n 



n 



hoiSS 



no 



A-B 



Fig. 150. 

 A-E groups of beans representing five pure lines. Below A-E the 

 group formed of the combination of the other five. (After Johann- 

 sen.) 



critical experiments to determine whether individual dif- 

 ferences shown by the beans are affected by selection. 

 If selection changes the character of the individual, it 



