84 EVOLUTION AND GENETICS 



exactly the same as Mendel's postulated elements. 



Mendel's second law for the inheritance for two 

 or more characters also finds its explanation in the 

 behavior of the chromosomes, provided the members 



Red 



II 



Parents 



White 



I 



Germ cells 

 of parents 



10 



Hybrid (F^) 



Sperm 



(Fp) red 



wnite 



Fig. 36. — Diagram to illustrate the distribution of the chromo- 

 somes in a cross between a red and a white four o'clock (see fig. 

 17). The chromosomes that carry the gene or factor for red are 

 here black, and those that carry the gene for white are w^hite. 



of the pairs of chromosomes are sorted ont indepen- 

 dently of each other (fig. 37). For example, in the 

 cross between yellow-round and green-wrinkled 



