CLASSIFICATION OF BACTERIA. 



21 



Many bacteria have the power of motion which is pro- 

 duced by slender motile hairs arising from their body and 

 which by lashing to and fro produce a locomotion ( Fig. 5 ) . 



FIG. 5. 



Bacilli showing flagella. (Migrila. 



These hairs are called flagella. They are sometimes numer- 

 ous and scattered all over the body (Fig. 5, a), sometimes 

 few and grouped at one or both ends (Fig. 5, b), and in 

 other cases only a single flagellum is found (Fig. 5, c). In 

 many bacteria they are entirely wanting. 



By the use of these characters bacteria are divided into 

 three easily recognizable divisions: 



i. Spherical Bacteria. Coccus. This group includes all 

 bacteria which are spherical. They are further subdivided 

 in accordance with their method of division. In some of 

 them the successive divisions follow one another in the same 

 plane. If the spheres break away from each other after 

 division, separate spheres, of course, arise, but it frequently 

 happens that they remain clinging together for a time after 

 divi-sion, so that long chains are produced (Fig. 6, a). In 

 other cocci the second division plane is at right angles to 

 the first (Fig. 6, b). In these cases, if the spheres remain 



