172 OUTLINES OF EVOLUTIONARY BIOLOGY 



diagram A represents an unreduced nucleus composed of sixteen 

 ids, eight paternal and eight maternal, all the paternal and all the 

 maternal ids respectively heing supposed to be alike. After 

 reduction and union with another mature germ cell containing 

 also only one kind each of paternal and maternal ids, but both 

 differing in some respect from those of its mate, the nucleus of 

 the next generation will contain four kinds of ids, two paternal 



FIG. 78. Diagram illustrating the Composition of the Germ Plasm 

 (Chromatin Substance of the Nucleus) out of Ancestral Ids, and the 

 Effect thereon of repeated Amphimixis. (From Weismann's " Evolution 

 Theory.") 



A D the unreduced nucleus, containing sixteen chromosomes (each consisting of a 

 single id), of four successive generations. In A the germ plasm consists of only two 

 kinds of ids ; in I? of four ; in C of eight, and in D of sixteen. mJ, pJ, maternal 

 and paternal ids. 



and two maternal, as shown in B, while in the next generation 

 there ma}^ be eight kinds, as shown in C, and in the next sixteen, 

 as in D. 



We must, then, in accordance with the views of Weismann, 

 look upon the germ plasm of any one of the higher organisms as 

 being made up of a larger or smaller number of ids, each one 

 representing the inheritance received from some more or less 

 remote ancestor on the paternal or maternal side, though of course 



