20 LORANDE LOSS WOODRUFF 



tion in size during each period clearly indicates that the cell 

 may function normally in diverse size relations (parts B and C), 

 and that the inciting cause of cell division must be sought in 

 other factors. The fact that cells of a protozoan genotype show 

 great size differences which bear no direct relation to division is 

 of great significance as it indicates clearly that the conditions 

 which induce growth may be distinguished from those which 

 incite fission. 



The data presented also indicate that the mean proportion of 

 nuclear to cytoplasmic material is smaller as the rate of repro- 

 duction wanes {B and C) and thus are in agreement with those 

 of Moody's study of Spathidium. This result is contrary to the 

 observations of Hertwig and his school though it is, at first 

 glance, in agreement with Minot's nucleo-cytoplasmic concep- 

 tion of cytomorphic changes leading to senility. But Minot's 

 theory, if I interpret it correctly, does not include cases of physio- 

 logical degeneration other than those brought about by an inher- 

 ent tendency to 'grow old,' and consequently, since the present 

 data concerns cells which are degenerating as a result of their 

 environment, the results only indirectly bear on his theory. 



When we survey the results of the already numerous investi- 

 gations on cell size and nuclear size and their relation to each 

 other in the cell complex, one cannot fail to be impressed with 

 the fact that the data are remarkably diverse and contradictory 

 — much more so than would, a priori, be anticipated if the Kern- 

 plasmarelation idea were substantially sound. To cite but a 

 single instance, the results of Popoff on Stylonychia mytilus and 

 my own on Oxytricha fallax may be considered. These two 

 races of closely related hypotrichous ciliates were bred under 

 conditions which should render them directly comparable, and 

 each ended with the extinction of the lines after a considerable 

 number of generations. Yet the cytoplasmic change in Stylo- 

 nychia consisted in an unmistakable decrease as the division rate 

 decreased, while that of Oxytricha showed an equally marked 

 increase as the rate of division waned. In each there was nuclear 

 enlargement with falling divisional activity — but obviously the 

 decreased cytoplasm resulted in an increase in the proportion 



