206 Regulation of Size in Unicellular Organisms 



The coefficient of variation of this series of cells is 9.7 

 per cent. 



A smaller series of measurements of size eccentrici- 

 ties between daughter cells was made by Baas-Becking 

 and Baker ('26). In their 52 pairs of cells the coeffi- 

 cient of variation was only 2.1 per cent. 



The accuracy with which two daughter cells are 



120 



100 



80 



T3 



<v 



3 



CD 



£ 60 

 g-40 



£0 



5 10 15 20 25 30 35 



Difference of length in per cent of length 



Figure 66. Differences in length between sister cells of Spirogyra maxima 

 at the time of fission. Circles represent the actual frequency at each per 

 cent of difference; black squares represent the same data averaged for each 

 five per cent. The line as drawn represents a probability curve, whose 

 coefficient of variation is 9.8 per cent. (Data of Van Wisselingh, '20). 



equally endowed with substance has, therefore, a 

 standard error of two to ten per cent. Sister cells are 

 unlike in size at their very formation; at the beginning 

 of their independent lives. Not all size diversities are 



