CELLS OF BACILLUS MEGATHERIUM 77 



culture for inoculation, hoping thus to get a lag period uncomplicated 

 by spore germination. This hope, however, was not fulfilled, lag 

 being absent. Culture V received one-tenth, and Culture VI one- 

 hundredth as many cells as Culture IV. 



From these broth cultures it is quite apparent that the changes 

 in cell size are not nearly so extensive as those observed in the 

 preceding agar culture; but also the rate of growth is much lower. 

 In the agar culture (Culture I) the mean generation time for the 

 first twelve hours was sixty-eight minutes; in Culture II, it was 

 317 minutes; in Culture III, 153 minutes; Culture IV, 223 minutes; 

 Culture V, 111 minutes; Culture VI, 78 minutes. The maximum 

 size attained in these cultures was as follows: Culture I, 19.8[/.; Cul- 

 ture II, 8.5; Culture III, 9.7; Culture IV, 7.5; Culture V, 8.0; 

 Culture VI, 8.6. It is apparent, then, that the size attained depends 

 upon the actual rate of growth in the culture, the shorter the genera- 

 tion time the greater being the length of the cells; but since these 

 experiments were not all run under exactly the same conditions, 

 this correlation is of course not a perfect one. The relationship of 

 the size of the cells to the rate of growth is more clearly apparent by 

 consulting the graphs in Figures 17 and 18 (the data for which may 

 be found in Tables VIII, IX and X), which show the growth curves 

 and the curves for the size of cells in Cultures II and III. The 

 more heavily seeded culture (II) shows a lower growth rate, as 

 indicated by the slope of the curve during the logarithmic growth 

 phase, than Culture III, and correspondingly the curve for cell size 

 reaches a lower maximum and declines more rapidly than in the 

 culture (III), which was seeded with one-tenth as many cells. The 

 same thing was found to be true in Cultures IV, V and VI (data 

 for which will be found in Tables XI, XII, XIII, XIV), the curves 

 for cell size being somewhat irregular, but again the maximum was 

 higher in Culture VI, which was most lightly seeded, and this size 

 was maintained for a longer period of time. 



Corresponding with the difference in actual size of the cells in 

 these broth cultures, there was found a distinct difference in the de- 

 gree of variation in size. For Cultures II and III the frequency 

 curves are presented in Figures 19 and 20. It is apparent at once 

 that in neither culture were the changes in the form of the distribu- 



