178 Regulation of Size in Unicellular Organisms 



tial numbers of measurements, the exact volume of 

 cytoplasm which must accumulate before each nucleus 

 began to divide was calculated. 



Excision of cytoplasm. The effect upon the size of 

 the nucleus of removing cytoplasm has been studied in 



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Number of nuclei per individual 



Figure 59. Correlation between cube of diameter of shell and the number 

 of nuclei, in two lines, A and B, of one clone of Arcella polypora. The 

 most divergent point (in A) represents only two individuals. (Data of 

 Hegner, '20b, pp. 49 and 50). 



a number of species. In a few instances studied by 

 Popoff ('08), Frontoniae which were cut early in their 

 individual growth were found not to decrease the ab- 

 solute sizes of their nuclei. The cytoplasms under- 

 went prolonged growth, so that the customary adult 



