BACTERIA 19 



being in one jelly-like lump. This is termed a zooglea (C>ov, 

 animal, /A9, glue) (Fig. 2). 



Locomotion. Many bacteria possess the faculty of self- 

 movement, carrying themselves in all manner of ways across 

 the microscopic field some very quickly, others leisurely. 



Vibratory Movements. Some bacteria vibrate in them- 

 selves, appearing to move, but they do not change their place; 

 these movements are denoted as molecular or "Brownian," 

 and are due to purely physical causes. 



Flagella. Little threads or lashes are found attached to 

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



a b c 



Fig. 3. Types of flagella: a, Vibrio cholerae, one flagellum at the end 

 monotrichia type; b, Bacterium syncyaneum, tuft of flagella at the end, rarely 

 at the side lophotrichia type; c, Bacterium vulgare, flagella arranged all 

 about peritrichia type (Lehmann and Neumann). 



sides sometimes only one, and on some several, forming a 

 tuft. 



These flagella are m constant motion, and can probably be 

 considered as the organs of locomotion; they have not 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.) Flagella serve some- 

 times to increase food-supply, and have been found on some 

 species which are non-motile. 



Reproduction. Bacteria multiply through simple division 

 or fission, as it is called. Spore formation is simply a resting 

 stage and not a means of multiplication. To accomplish 

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

 middle, the cell-wall indents itself gradually, forming a septum 



