BACTERIA. 19 



ment, carrying themselves in all manner of ways across the 

 microscopic field, some very quickly, others leisurely. 



Vibratory Movements. Some bacteria vibrate in themselves, 

 appearing to -move, but they do riot change their place ; these 

 movements are denoted as molecular or " Brownian." 



FIG. 2. 



Zooglcea. 



Flagella. Little threads or lashes are found attached to many 

 of the motile bacteria, either at the poles or along the sides, 

 sometimes only one, and on some several, forming a tuft. 



These flagella are in constant motion and can probably be 

 considered as the organs of locomotion ; they have not yet been 

 discovered upon all the motile bacteria, owing no doubt to our 

 imperfect methods of observation. They can be stained and 

 have been photographed. See Fig. 3. 



Reproduction. Bacteria multiply either through simple divi- 

 sion or through fructification by means of small round or oval 

 bodies called spores from spora-seed. In the first case, division, 

 the cell elongates, and at one portion, usually the middle, the 

 cell-wall indents itself gradually, forming a septum and dividing 

 the cell into two equal parts, just as occurs in the higher plant 

 and animal cells. See Fig. 4. 



