RANGE AND DISTRIBUTION OF MICROBES. 35 



thirty minutes, it is evident that the rate of numerical increase, under favor- 

 able conditions, is very great. Allowing thirty minutes for each septation, 

 there would b^ a colony of 2,097,152 microbes in ten hours, developed from 

 a single cell, or about 75,000,000,000,000 cells in twenty-four hours. 

 However, under natural conditions septation never proceeds in such uniform 

 ratio. All manner of checks to septation come into play sooner or later 

 which may finally bring about complete cessation of septation and sporulation. 



