CLASSIFICATION OF BACTERIA 



105 



Rod-shaped bac- 

 teria. 



Rod-shaped Bacteria. These are in the shape of rods 

 of greater or less length. They are usually somewhat 

 rounded at the ends and may be only a little longer than 

 they are broad, or they may be Q 

 very many times as long as broad 

 (Fig. 50). When one of these grows 

 it lengthens and commonly soon 

 divides into two, but they may con- 

 tinue to lengthen for a time without F IG. 50. 

 manifesting any signs of division. 

 In such a case they form long slender threads, as shown 

 in Fig. 50, b. These threads, however, eventually break 

 up -into short sections (Fig. 50, c). Some of these rod- 

 shaped bacteria have flagella and are capable of active 

 motion, in which case they form the species of Bacillus 

 (Fig 48, c) ; others have no flagella and are quite with- 

 out the power of motion, in which case they constitute the 

 species Bacterium (Fig. 48, d). 



Spiral Bacteria. A third type of bacteria is in the form 

 of a spiral rod, shown in Fig. 51. These, however, are 

 somewhat uncommon and of less 

 importance than the others. Like 

 the other forms they may possess 

 flagella or they may be without 

 them. 



Multiplication. The growth and 

 multiplication of bacteria is ex- 

 tremely simple and consists in a 

 lengthening of the individual followed by its division. A 

 sphere becomes slightly oval in shape and then divides in 

 the middle to produce two spheres, as shown in Fig. 52, a. 



FIG. 51. Spiral bacteria. 



