WHAT EVOLUTION IS 133 



indicated by the white circle and the 

 black circle in the diagram over the 

 representative of this generation. In 

 consequence of the dominance of 

 black over white, all individuals, in 

 this generation, will have black coats. 

 But since they arise from a germinal 

 mixture, each of these individuals 

 will be able to produce two kinds of 

 germ cells, the males white sperm and 

 black sperm, and the females white 

 eggs and black eggs. If, now, we 

 assume that the two kinds of eggs 

 are produced in equal numbers and 

 that the same is true of the sperm and 

 that the union of egg and of sperm is 

 purely fortuitous, the kinds of guinea 

 pigs and their proportionate num- 

 bers, as already stated for the second 

 descendent generation, will be ex- 

 actly realized. For with two kinds of 

 sperms and two kinds of eggs, there 

 will be four possible combinations in 



