IMPORTANCE OF ID-REDUCTION 51 



The reduction which precedes maturation may vitally affect 

 the constitution of a germ-cell ; for just as chance leaves in 

 a matured germ-cell, after division of the chromosomes, a 

 majority or a minority of X determinants of a particular varia- 

 tion, so will the matured cell tend to develop a plus or a minus 

 variation of the organic character represented by these deter- 

 minants. Moreover, a germ-cell which contains a majority 

 of plus variations of X determinants may, as the result of 

 amphimixis, unite with another germ-cell having likewise a 

 majority of plus variations of the same determinants ; and the 

 result will be a change in the determinate X in the soma. In 

 the same way, if two germ-ceUs, which contain each a minority 

 of X determinants, should unite, the determinate X will likewise 

 be altered, but in a direction opposite to that of the previous 

 instance. 



It will be seen from this example that the reduction of the 

 ids in the maturation divisions is a highly important pheno- 

 menon in the process of evolution. It must be remembered 

 that it is not a single id that determines the character of an 

 organ, but a majority of the ids in the germ-plasm. Every id 

 contains in fotentia aU the characters of the organism, and it 

 is only by the modification of the majority of determinants of 

 the whole idant — i.e., of the determinants in the majority of the 

 ids — that the somatic determinate can be modified, either in 

 the direction of a plus or of a minus variation. To take a case 

 of sexual dimorphism, if the males with the most variegated 

 plumage are successful, then a majority of determinants A^, 

 corresponding to the plumage A, must be handed down in the 

 inheritance in order to secure a continued somatic effect ; and 

 the oftener such a majority of determinants A^ are brought 

 together, the less chance there is of this majority being reduced 

 to a minority as the result of the halving of the ids. 



The phenomena which accompany maturation have as ultimate 

 result the reduction of the total number of ids in the germ- 



4—2 



