Heredity 167 



A + A = A\ 

 A + B = AB. 

 B +A = BA. 

 B + B = B\ 



A 2 and B 2 are equivalent only to A and B. Since both 

 of the opposed or contrasted characters cannot be visible 

 at the same time, we have the following : 



B 



in which small 6 represents the character that for the 

 time being is not able to express itself, or is recessive, and 

 large B represents the same character fully expressed. 



In these gametes, the unit-characters of the plants that 

 bear them are pure. Even in hybrid plants the pollen- 

 grains and the egg-cells are not hybrids. According to 

 the hypothesis of gametic purity, therefore, hybrids 

 follow natural and numerical laws; but these laws are 

 always obscured by new crossing. True intermediate 

 characters do not occur. If new characters appear, it is 

 because they have been recessive or latent for a genera- 

 tion, or because the plant has varied from other causes ; 

 they are not the proper results of hybridization, unless 

 they are due to a reconstruction of characters. We may 

 suppose that a new character that appears because of 

 some internal change may be impressed on the gametes 

 and thereby be perpetuated. The results of hybridiza- 

 tion, according to the mendelian view, are not funda- 



