34 Regulation of Size in Unicellular Organisms 



Table 3. 

 Relative Progressions of Body Volume, Number of Individuals, and 

 Total Protoplasmic Bulk in a Broth Culture of Bacillus 

 Coll (Data of Henrici, '23). See also Figure 46 



lation in the organisms of any substances taken from 

 the medium could only be accomplished by relative 

 dehydration of the body substance. 



These data for B. coli are altogether comparable 

 with the data for B. ramosus cited above; the only 

 difference lies in the unessential fact that in B. ramosus 

 the individuals remained in filaments instead of sep- 

 arating. But the results differ greatly. 



Studies of increase of bulk in yeast populations 

 were made by Balls and Brown ('25) and Richards 

 ('28a). Only with respect to bulk, and not with re- 

 spect to mere numbers of individuals was the progres- 

 sion logarithmic. 



Some results upon the increase of bulk in the green 

 organism Scenedesmus costulatus, obtained by Roach 

 ('26), deserve special mention. These algae increase 

 in size for two or three days, at 24.4°, and then sud- 

 denly divide into four or eight progeny. In the cul- 

 tures studied, enough of the individuals divided syn- 

 chronously to cause the average body volume to fluc- 

 tuate in three-day rhythms. When the concentration 

 of the cells or the number in the culture was estimated, 

 there were converse fluctuations in the rate of mul- 

 tiplication. But when average volume was multiplied 

 by number of cells present, then the increase (of pro- 



