Rates of Growth of Individuals 33 



growth employed the cylinders were 1.75 micra in 

 diameter. 



Figure 15 shows that under good cultural conditions 

 growth in length was uniform in rate, regardless of the 

 number of cells present in one filament; for in this 

 figure the lengths are plotted logarithmically. But 

 when measured more frequently it was found (figure 

 16) that growth was retarded each time fissions oc- 

 curred. For a single cell generation the volume curve 

 would then tend to resemble the curves for growth in 

 length of a Paramecium. 



It is obvious that the true rate of growth for a single 

 individual could be described only from observations 

 made at intervals of one or two minutes. 



Some other bacteria. Similar measurements have 

 been made occasionally upon other bacteria. One 

 series was obtained by Schmalhausen and Bordzilow- 

 skaja ('26) upon numerous living individuals of three 

 species, Proteus vulgaris, Bacillus coli, and Bacillus 

 dysenterise Shiga-Kruse. They believed that the vol- 

 umes were proportional to the lengths in these three 

 species. In all three the averaged lengths increased 

 linearly throughout the ten hours required for one 

 generation. 



Growth in bulk of populations. Some data of Hen- 

 rici ('23) may be utilized to tell something about the 

 growth in bulk of bacterial masses. Henrici measured 

 the average sizes of Bacillus coli at various times after 

 inoculating a fluid culture, and also counted their re- 

 lative numbers (table 3). Within the first three hours 

 the volume per individual appears to have increased 

 eight times, and the total bulk of bacterial body-sub- 

 stance in the culture increased eighty times. The table 

 also shows that no further increase of total bulk occur- 

 red within the next nine hours. From this it may be 

 inferred that within this nine-hour period the accumu- 



