What Bacteria Do 19 



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 

 fiercely as ever it did among more highly or- 

 ganized beings. One race succeeds another, 

 one species adapts itself to the conditions 

 which brought about the extinction of its 

 predecessors. Hardy individuals struggle with 

 their weaker neighbors as the food grows scanty 

 in their microscopic seas, and the weaker goes 

 to the wall. 



Many forms possess the power of living and 

 multiplying in the manner described above so 

 long as the proper conditions prevail, but when 

 life, owing to some change in the environment 

 becomes no longer possible, the vital powers 

 collect themselves in a little shining mass in 

 one end of the bacterium, which surrounds 

 itself by a dense membrane, and in this form, 

 which is called a spore, Fig. 3, it can survive 

 adverse conditions which in the ordinary form 

 would have destroyed its life. Restore it 



