1 8 THE STORY OF THE BACTERIA. 



an eminent biologist that, if the proper condi- 

 tions could be maintained, a little rod-like 

 bacterium, which would measure only about a 

 thousandth of an inch in length, multiplying 

 in this way, would in less than five days make 

 a mass which would completely fill as much 

 space as is occupied by all the oceans on the 

 earth's surface, supposing them to have an 

 average depth of one mile. 



Let not the timid soul tremble, however, for 

 the principles of the survival of the fittest and 

 the influences of environment have kept our 

 prolific organisms so well in check that the 

 world had grown very old and its favored 

 nursling, man, pretty well along in experience 

 and skill before ever he recognized the exist- 

 ence of these his microscopic contemporaries 

 and possible ancestors. 



The struggle for existence goes on where 

 varying forms of bacteria are growing' as fierce- 

 ly as ever it did among more highly organized 

 beings. One race succeeds another, one spe- 

 cies adapts itself to the conditions which 

 brought about the extinction of its predeces- 

 sors. Hardy individuals struggle with their 



