MENDELISM 13 



The tall and dwarf pea crossed could be illustrated 

 thus, together with the germ-cells — 



• • o o 



produce 



• o 



According to Mendel, a germ-cell is either purely 

 dominant, or purely recessive, and never partly the one and 

 partly the other — always ooro, and never ©. 



I must apologize for repeating myself, but this is the 

 essence of Mendel's theory, and no progress can be made in 

 Mendelism without a clear appreciation of the constitution 

 of the germ-cells. 



As the character of a plant depends upon the nature of 

 the germ-cells from which it has sprung, it follows that the 

 Fj generation must resemble the dominant parent, and that 

 a tall pea crossed with a dwarf must produce tall offspring ; 

 but as the hybrids possess two kinds of germ-cells, their off- 

 spring are not of one kind only : some are tall, and others 

 are short (in the Fij generation). 



So far, we have seen that Mendel established the fact of 

 dominance ; and, secondly, he assumed that hybrids contain 

 germ-cells similar in character to those of both parents. 



How did he explain the 3 to 1 ratio in the Fij generation ? 

 Now we come to another important doctrine of Mendel — 

 another stroke of genius. Mendel concluded that not only 

 are both dominant and recessive germ-cells produced in the 



