External Factors and Size 



149 



Yeast. Similar changes of volume have been demon- 

 strated in yeast. Paine ('11) studied the progression 

 of cell volume with time, when the yeast individuals 

 were transferred to very strong solutions of several 

 substances. The results in two solutions which gave 

 contrasting size modifications are represented in figure 

 51. In less than one hour the body volumes dropped 



CD 

 CD 



E 



O 



> 



§90 

 PQ I 



Q01 0.02 0-03 0.04 



Concentration of NaCI 



0.05 



Figure 50. The influence of various concentrations of sodium chloride 

 (made up in hay infusion) upon body-volume (calculated as / X b 2 ) in a 

 clone of Paramecium caudatum. Each point represents the average of 50 

 individuals which were fixed at the end of 48 hours in the solution, within 

 which time fission occurred on the average once in each of the original 

 animals. Concentration is expressed as molar. (Data of Estabrook, '10). 



very greatly; how greatly we cannot tell. Thereafter 

 the individuals in the urea solution recovered their 

 original volumes and maintained them ; but those in the 

 sodium chloride solution recovered only slightly, and 

 later shrank further. It is possible that the differences 

 in the various solutions were due in part to modifica- 

 tions in the rate of multiplication of individuals with 

 time, for the body volumes were reckoned from hema- 

 tocrit determinations that were carried out upon cul- 



