202 Regulation of Size in Unicellular Organisms 



accurately regulated than the volume. Gerassimow 

 ('02) based his comparisons upon the mean for each 

 dimension, with the result shown in table 15. The 

 same relation would be reached by comparing the 

 modes, except in the case of cell volumes, where there 

 was no distinct mode. The conclusion is that the lat- 

 eral cell surface is proportional to the nuclear volume, 

 and not the total cell surface nor the total cell volume. 

 The lateral cell surface in Spirogyra is characterized 

 by having a number of ribbon-like spiral bands of chlo- 



Table 15. 



Relative Mean Dimensions of Normal, Double-Nucleated, and Two- 

 Nucleated Cells of Spirogyra. (Data of Gerassimow 



'02, p. 233.) 



Two 



If volume of nucleus is 

 Length of cell 

 Volume of cell 

 Lateral surface of cell 

 Total surface of cell 



1. 



0.08 

 885. 

 31.2 

 45.3 



rophyll. Gerassimow ('02) counted the number- of 

 complete spirals in these bands and reached the result 

 that the number was nearly twice as great in the bi- 

 valent cells. He also counted the number of pyrenoids 

 or centers of starch formation in each ribbon of chloro- 

 phyll, arriving at the result that double-nucleated cells 

 had 204 per cent and two-nucleated cells had 181 per 

 cent of the number in single-nucleated cells. Thus on 

 the average the number of pyrenoids was proportional 

 to the nuclear mass, and to the lateral cell surface. 

 In the cases of the cytoplasmic or cellular surface, 

 , the chlorophyll bands, and the pyrenoids, it is evident 

 that their quantity was conditioned directly by the 

 amount of nuclear material present, because half of 

 all the original cell contents except the nucleus went to 

 form a non-nucleated cell at the time of the irregular 



