186 



THEORY OF EVOLUTION 



tween parent and offspring. If this is correct, 

 and if in the protozoa the chromatin has the 

 same influence that it seems to have in higher 

 animals, the mode of reproduction in Difflugia 

 would be expected to give little more than ran- 

 dom sampling of the germ plasm. 



Jennings was able by means of selection to 

 get from the descendants of one original indi- 



FIG. 92. Races of Difflugia. (After Leidy.) 



vidual a number of different types that them- 

 selves bred true, except in so far as selection 

 could affect another change in them. In this 

 connection it is interesting to note that Leidy 



