22 HOUSEHOLD BACTERIOLOGY. 



The spiral forms also may remain in one colony or 

 break up into single cells after division. 



Sometimes they 

 unite their bodies 

 by a gelatinous 

 film to form a 

 slime over the sur- 

 face of whatever 

 FIG. is. ZOOGLOEA OR THE they are growing 



FILM-FORMING BACTERIA. ' 



upon, as seen on 



the walls of the waste pipe of the refrigerator or on 

 the surface of the water in the pan. This is known 

 as a zoogloea form. Fig. 13. 



Rapidity The rapidity with which they reproduce depends 

 largely upon the food supply, the warmth and moist- 

 ure that is, whether the conditions of life and 

 growth are favorable. 



In this prolific reproduction lies their great power 

 for harm or benefit to the world. 



In some species, under favorable conditions, a new 

 generation is born oftener than every half hour. If 

 this rate were continued for a day, one bacterium 

 might become ancestor of over sixteen million de- 

 scendants. Some interested observer has calculated 

 that in two days the billions thus born would fill a 

 pint measure and weigh a pound, while in another 

 twenty-four hours their weight would equal eight 

 thousand tons. 



These numbers, however, are of no practical im- 



