224 MENDELISM 



instance, when the non-development of pigment leads 

 to the appearance of white flowers. 



We can now realize how necessary it is, in order to 

 avoid hopeless confusion, to follow the behaviour of 

 each pair of characters in the offspring separately. 



The result of the meeting between the two opposed 

 characters of the same pair we saw to be different in 

 different cases. There may arise in the offspring 

 (i) the appearance of a simple blend of the two parental 

 characters. Or (2) one character may be more or less 

 dominant over the other. Or (3) the combination of 

 the two parental characters in the offspring may give 

 rise to an appearance quite different from that of either 

 of them, very much in the same way as in chemistry 

 oxygen and hydrogen when combined give rise to water. 

 Or (4) we may get further complications in which un- 

 suspected characters, present in an invisible condition 

 in one or both parents, take a part, often giving rise 

 to the appearance of a supposed reversion. 



The most important phenomenon of all, however, 

 is that which is found to occur at the formation of the 

 germ cells of the heterozgyote plant or animal. What- 

 ever the appearance of the hybrid form may have been, 

 at this stage in its history the determining factors for 

 each member of the pair of parental allelomorphs 

 reappear in their entirety in certain cells which by 

 their division give rise to the gametes, and at one 

 of the divisions in question the parental characters (in 

 a potential condition) separate completely from one 

 another, so that half the gametes bear one allelomorph 

 and half of them the other. In cases where more than 



