150 Regulation of Size in Unicellular Organisms 



tures which were initially equivalent in being inocu- 

 lated with similar samples. Paine believed that the 

 urea entered the bodies, while NaCl did not, which is 

 the customary assumption made in plasmolysis ex- 

 periments. 



105 



CD 



£100 



ZJ 



o 

 > 



z. 



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o 



35 



90 



-85 



CD 

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£80 



75 







8 12 16 



Time in hours 



20 



24 



Figure 51. Progressive effect of molar solutions of urea and of sodium 

 chloride upon the relative volumes in Saccharomyces cereviseae. The 

 volumes were measured by a hematocrit. (Data of Paine, '11). 



The amount of shrinkage of yeast in various con- 

 centrations of sodium chloride was determined by 

 Drabble et al. ('07). In this work the diameters of 

 individual cells were measured. As shown in figure 52, 

 the shrinkage was greater with each increment of con- 

 centration. Apparently all the samples of yeast were 

 measured within the same time limits, but in the light 



