268 PHYSIOLOGY OF BACTERIA 



siderable variability of the growth rate, some of them 

 dividing four to five time units later than the others. 



This computation is an over-simplified case, making several 

 assumptions which are not probable. For example, this computation 

 assumes, that all genes multiply at the same rate, and that a cell 

 divides as soon as the last gene has doubled while we know that, 

 with higher organisms at least, some time elapses after chromosome 

 division before cell division occurs. 



/ 2. Z t 5 6 7 8 9 fO ti 12. a f¥ tS /6 



Fig. 26. — Percentage of cells dividing in successive time units computed for 

 g = 0.5, and for various numbers of genes, g. 



The observed facts (Kelly and Rahn, 1932) agree 

 with the theory in a general way. Bad. aerogenes as well 

 as Sacch. ellipsoideus showed a great variability of 

 growth rate. Table 74 shows three series of data 

 with Bad. aerogenes. The frequency curve is skewed to 

 the left as in the theoretical curve of Fig. 26. The 

 results with yeast corresponded to the data computed for a 

 larger number of genes while Bad. aerogenes appears to 

 have a smaller number. A special investigation showed 

 that the offspring of the most rapidly multiplying 

 individuals was not rapid, but average, and the same was 

 true with the progeny of the slowest cells. 



