10 20 30 40 50 60 70 80 SO 100 



Lateral surface m thousand square micra 



Figure 65. Frequency of size among 26,596 cells of Spirogyra bellis. A, 

 normal cells ; B, cells with one double-sized nucleus ; C, cells with two nuclei. 

 The doubling of the nuclei was produced by previous exposure to low 

 temperatures. The mean sizes are in each curve represented by vertical 

 lines. (Data of Gerassimow, '02, p. 229). 



