What Bacteria Do 17 



and so on through varying phases of move- 

 ment until the head swims and the eye tires in 

 following them. This move- 

 ment, in some of the bac- 

 teria at least, is induced by 

 a little hair-like projection 

 from the end of the organ- FIG. 2. FLAGELLA 



1 M -11 OF BACTERIA 



ism, which vibrates rapidly 

 to and fro Fig. 2. It is very difficult to 

 see these little projections or flagella, even 

 with the most powerful microscopes, but, 

 notwithstanding this, they have actually 

 been photographed, and in some cases 

 the image of the flagella, which failed to 

 make an impression on the retina, has been 

 caught and fixed by the sensitive plate in the 

 camera. 



Warmth, moisture, oxygen, and some or- 

 ganic matter are the simple conditions re- 

 quired for the activities of the bacteria. 



When the conditions are favorable they may 

 increase in number to a degree which is limited 

 only by their surroundings. A little constric- 

 tion appears around one of the bacteria; it 

 grows a little longer, a partition forms across 



