HEREDITY 



in Fig. 34. The nature of the gametes formed 

 by the parents crossed is shown in the first row ; 

 the composition of the F^ individuals, immedi- 

 ately below. In the two lower rows are shown 

 four different sorts of gametic splittings which 

 may occur in the F^ individuals, producing thus 

 eight different kinds of gametes. If, in re- 

 ality, the Fi individuals form eight kinds of 

 gametes, all equally numerous, and chance 

 unions in pairs occur among them, there should 

 be produced eight corresponding sorts of indi- 

 viduals numerically as 27 : 9 : 9 : 9 : 3 : 3 : 3 : 1. 

 In a total of 64 individuals there should be on 

 the average one pure individual in each of the 

 eight different classes. The class numerically 27 

 in 64 manifests three dominant characters ; those 

 which are numerically 9 in 64 manifest two domi- 

 nant characters ; those which are numerically 3 

 in 64 manifest one dominant character. Among 

 each of these there will be on the average one 

 pure individual, but the class which contains 1 

 individual in 64 is a pure recessive, for it contains 

 no dominant character. This combination, then, 

 requires no fixation. It will breed true from the 

 start. 



50 



