GROWTH OF BACTERIA 107 



spores are capable of subsequently germinating into 

 new individuals like those that produced them and thus 

 continuing the race (Fig. 53, b). 



Not all bacteria produce spores, and the question 

 whether any species of bacteria forms spores is a matter 

 of most extreme significance in connection with its func- 

 tions ; for these spores are covered by a little shell which 

 is hard and tough and capable of 

 resisting various adverse condi- 

 tions. Spore-bearing bacteria 

 may be dried without injury, for 

 their spores protect them from 



destruction. They may be heated ^^'^f^^^ '--^'^ 

 to a high temperature, even to 

 boiling, without being killed. -^- 



Thus the presence of spores will f,(,. 53. showing the forma- 

 make a great difference in the tion of spores. At 3 is a 

 ease with which any material can ^""^^ «P°™ a"'* ^' * ^ g«™'- 



, .,.,,, _ . nating spore. 



be sterilized by heat. Bacteria 



not capable of producing spores are very easily killed by 

 heat, while the spore-bearing forms are destroyed with 

 much greater difficulty. 



Growth of Bacteria 



Rapidity of Growth. The most striking fact in regard 

 to bacteria is their wonderful rapidity of multiplication ; 

 for upon this are dependent their extraordinary powers. 

 Bacteria growth and multiplication mean the same thing, 

 and the rapidity with which they can multiply is almost 

 inconceivable. Certain, kinds of common bacteria can 



