OBSERVATIONS OF DIPHTHEROID BACILLUS 105 



of the cells of the Corynebacteria which they observed. It is note- 

 worthy that their curves also show a very slow increase to the original 

 size of the cells as compared with the very rapid decrease to the 

 original size observed in the other organisms studied. It is evident 

 that more work will have to be done with this group before the 

 changes in cell size can be clearly correlated with the phases of 

 growth. From the curve here submitted it would seem that the 

 small sized cells are more characteristic of the resting phase than 

 of the growth phase, but from evidence to be submitted later it is 

 suggested that this may be wrong. 



That this diphtheriod organism behaves differently from the 

 other bacteria studied with regard to its variations in cell size is 

 still more apparent when studied from the standpoint of frequency 

 distributions, illustrated in Figure 29. No such pronounced varia- 

 tion is apparent as was the case with B. megatherium and the colon 

 bacillus; and the increased variation occurs not during the period 

 of most active growth, but during the resting period. The frequency 

 curves at six and twelve hours are practically symmetrical; all of 

 the others show some skewness. It will be noted from the coeffi- 

 cients of variation in Table XX that, while this value shows con- 

 siderable fluctuation, it is distinctly lower during the period from 

 nine to twelve hours, i.e., during the stage of decreasing size of 

 the cells, a period during which the growth rate is decreasing but 

 is still relatively high. While the cells are increasing in size again 

 during the resting phase, the coefficient of variation also increases. 

 It is clear, then, that variability in size is correlated with the actual 

 size of the cells, not necessarily with the rate of cell division. This 

 is notew^orthy because Taliaferro and Taliaferro have used the coeffi- 

 cient of variation as a measure of the rate of growth in trypanosomes, 

 on the supposition that during active cell division there will be found 

 more variation in size because of the presence in the population of 

 cells which are mature, cells. which have just divided, and all stages 

 between; whereas when growth ceases, there being no further cell 

 division,. all of the cells will be much of a size. This of course will 

 be true only if the cells show no other change in size than that 

 preparatory to division. However true it may be for trypanosomes, 

 it will not hold for bacteria. With the diphtheriod organism here 



