172 Regulation of Size in Unicellular Organisms 



from his measurements (figure 55) the correlation be- 

 tween body and nucleus is far from striking; most of 

 the measurements, however, were made upon individ- 

 uals which had just finished fission, and it is certain, at 

 least, that these were smaller both in nucleus and in 

 body than the older specimens. 



15 



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CD 

 DC 







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100 200 



Relative body volume 



300 



Figure 55. Correlation between nuclear volume and body volume in Para- 

 mecium caudatum. The volumes of the macro-nucleus and of the body are 

 calculated at / X b 2 . (Data of Hertwig, '89). 



Theory of fission. At the time, these measurements 

 seemed merely to demonstrate what might be expected, 

 namely, that large and small individuals were built 

 approximately in proportion. But in later years some 



