THEORY OF EVOLUTION 



183 



paramecium at each division, the genetic com- 

 position of parent and offspring should be the 

 same. Whether pseudo-parthenogenesis that 

 Woodruff and Erdmann have found occurring 

 in paramecium at intervals involves a redistri- 

 bution of the hereditary factors is not clear. 

 Jennings's evidence seems incompatible with 

 such a view. 



More recently one of Jennings's students, 

 Middleton, has made a careful series of selec- 

 tion experiments with Stylonychia (fig. 90) in 

 which he selected for lines showing more rapid 



FIG. 90. Stylonychia showing division into two. (After 

 Stein.) 



