Spirogyra Cells 203 



cell-division. The non-nucleated cells, Gerassimow ob- 

 served, lived many days, carrying on photosynthesis, 

 but not growing or reproducing. 



Gerassimow ('01) also gathered data to show when 

 and how the bivalent cells increased their sizes. In a 

 number of filaments he followed the increases of the 

 lengths and breadths of the bivalent cells and of sev- 

 eral neighboring normal cells. The first measure- 

 ments were taken two to five days after the treatment 

 with cold, and before the bivalent cells had divided; 

 second and often third measurements were made at in- 

 tervals of three to ten days thereafter. The relative 

 volumes found in one series of measurements, all of 

 which were begun upon two adjacent days, are plotted 

 in figure 64. It is seen that for normal and for en- 

 larged cells both growth, as expressed by the loga- 

 rithm of the volume increase, and cell reproduction, are 

 very nearly proportional to time. It is evident that the 

 bivalent cells grew faster only in the first few days; 

 that thereafter they merely multiplied their original 

 masses at the same rate as normal cells. In reaching 

 this conclusion it is somewhat disconcerting to find 

 that in both cases growth was slower in the first three 

 days of the measurements than later; the temperature 

 was not fully controlled, however, and in fact the ini- 

 tial delay of growth is not shown in measurements 

 which were started at other times. Indeed, Gerassi- 

 mow was very careful to compare growths only among 

 the various components of a single filament. He con- 

 cluded that the bivalent cells continued for many days 

 to have increased rates of growth, a conclusion hardly 

 justified by his data. Rather, after the initial process 

 by which the cytoplasmic surface was adjusted to the 

 nuclear mass, the enlarged cells approximately just 

 maintained their double sizes while they reproduced in 

 number and volume at the normal rate. 



