External Factors and Size 



143 



('19); three representative sorts of results are repro- 

 duced in figure 45. In most species the size increased 

 suddenly after transplantation to new medium, and 

 gradually decreased to the original level after twelve 



6 9 



Time in hours 



Figure 47. Progression of mean body length in Bacillus megatherium as 

 related to the age of the parent culture. At zero hours a culture was im- 

 planted from a 12-hour old parent culture. From this one, subcultures 

 were made at 2, 4, 6, and 8 hours ; individuals from each being fixed and 

 measured every hour. (Redrawn from Henrici, '24a). 



hours. But in B. diphtheriae and related organisms 

 the reverse was the case. 



Extensive analysis of these changes in bacteria has 

 been undertaken by Henrici ('23-'28). He first cor- 

 related the size changes with the rate of multiplication 



