152 Regulation of Size in Unicellular Organisms 



Drabble had already attained their equilibrium vol- 

 umes in the various solutions. 



In measurements of relative volumes at the end of 

 45 minutes, Seliber and Katznelson ('29) observed 

 shrinkages in various concentrations of NaCl which 

 were approximately half those found by Drabble. But 



0.1 0.2 0.3 0.4 0.5 0.6 Q7 08 



Molar concentration of NaCl. 



03 



1.0 



Figure 53. Effect of various concentrations of sodium chloride upon the 

 mean body volume of Pleurococcus vulgaris. The algae were placed in each 

 solution directly from the scrapings of tree trunks; and at least 15 minutes 

 elapsed before the diameters were measured. From 124 to 211 different 

 individuals were measured for each point. (Data of Drabble, Drabble, and 

 Scott, '07). 



in shape the curve was similar to figure 52. The time 

 factor proved to be important in such determinations 

 of yeast size, from the fact that very different size re- 

 lationships appeared when the organisms were al- 

 lowed to multiply in media of various concentrations 

 for one or more days. 



Green Algae. Drabble ('07) also measured the 

 changes of size in individuals of the green alga Pleuro- 



