WHAT ARE BACTERIA? 5 



fore, never seen in the microscopic preparations usually pre- 

 pared. They may be seen by special methods, but these are so 

 difficult that the beginner cannot use them satisfactorily. The 

 question of their motility is, however, usually determined with- 

 out staining, by the study of the living bacteria. (Exper. No. 

 30.) These flagella are differently distributed upon different 

 bacteria. Sometimes there is a single one on the end of a 



FIG. 4 FLAGELLA 



A. Peritrichic. B. Lophotrichic. C. Monotrichic. 



rod (Fig. 4, C) monotrichic; sometimes a small tuft at one 

 or both ends of a rod (Fig. 4, B) lophotrichic; and sometimes 

 there is a covering of flagella over the whole body of the 

 bacterium (Fig. 4, A} peritrichic. 



Multiplication of Bacteria. The most unique property of 

 bacteria is their almost inconceivable rapidity of multiplication, 

 and it is this which makes them of importance in nature. The 

 method of multiplication of bacteria is the simplest conceivable. 

 The organisms elongate a little and then break in two in the 

 middle, two individuals thus arising where there was formerly 

 one. Each of these now elongates and in turn breaks, and thus 

 by continued division the numbers increase. Figure 3, t and j, 

 shows this reproduction both in the rod and cocci forms of 



