246 BIOLOGY: GENERAL AND MEDICAL 



exhibited by the parents, and each member of such a 

 pair of characters is represented in an equal number of 

 germ cells of both sexes. Separate pairs of differen- 

 tiating characters (allelomorphs) conform to this law in 

 complete independence of one another. 



DeVries expresses Mendel's law in the following simple 

 language: "The pairs of antagonistic characters in the 

 hybrid split up in their progeny, some individuals re- 

 verting to the pure parental types, some crossing with 

 each other anew, and so giving rise to new generations of 

 hybrids. ... In fertilization the characters of both 

 parents are not uniformly mixed, but remain separated, 

 though most intimately combined in the hybrid through- 

 out life. They are so combined as to work together 

 nearly always, and to have nearly equal influence on all 

 the processes of the whole individual evolution. But 

 when the time arrives to produce progeny, or rather to pro- 

 duce the sexual cells through the combination of which 

 the offspring arises, the two parental characters leave each 

 other and enter separately into the sexual cells. From 

 this it may be seen that one-half of the pollen cells will 

 have the quality of one parent and the other the quality 

 of the other. And the same holds good for the egg cells. 

 Obviously, the qualities lie latent in the pollen and in the 

 egg, but ready to be evolved after fertilization has taken 

 place." 



According to Mendel's law, the unexpected appearance 

 in the offspring of characters not found in any but remote 

 parents may be accounted for by the presence of recess- 

 ive allelomorphs which have not until the present 

 generation been able to escape the dominance of the 

 opposed character. 



Mendel's discoveries regarding dominance are of the 

 greatest importance to every student of the problems 

 of heredity and are well synoptized by Castle thus: 



1. "The off spring of two parents, differing in respect of one 

 character, all resemble one parent and therefore possess the 

 dominant character, that of the other parent being recessive or 

 latent. 



