THEORY OF EVOLUTION 187 



has published figures of Difflugia (fig. 92) that 

 show that a great many "types" exist. If 

 through sexual union (a process that occurs in 

 Difflugia) the germ plasm (chromatin) of these 

 wild types has in times past been recombined, 

 then selection would be expected to separate 

 certain types again, if, at division, irregular 

 sampling of the germ plasm takes place. Until 

 these points are settled the bearing of these 

 important experiments of Jennings on the 

 general problem of selection is uncertain. 



How DOES NATURAL SELECTION INFLUENCE 

 THE COURSE or EVOLUTION? 



The question still remains: Does selection 

 play any role in evolution, and, if so, in what 

 sense? Does the elimination of the unfit influ- 

 ence the course of evolution, except in the nega- 

 tive sense of leaving more room for the fit? 

 There is something further to be said in this 

 connection, although opinions may differ as to 

 whether the following interpretation of the 

 term "natural selection" is the only possible 

 one. 



If through a mutation a character appears 



