24 ESSENTIALS OF BACTERIOLOGY 



sometimes to increase food-supply, and have been found on 

 some species which are non-motile. 



Reproduction. Bacteria multiply through simple divi- 

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

 resting stage and not a means of multiplication. To accom- 

 plish 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. 3.) 



Successive divisions take place, the new members either 

 existing as separate cells or forming part of a community or 





; -|t; 



Fig. 3. Division of bacteria: a, Division of a micrococcus; &, division of 

 a bacillus (after Mac6). 



group. It has been computed that if division takes place 

 every hour, as it often does, one individual in twenty-four 

 hours will have 7,000,000 descendants. 



Spore Formations. Two forms of sporulation, eiido- 

 sporous and arthrosporous. 



Endosporous. First, a small granule develops in the pro- 

 toplasm of a bacterium ; this increases in size, or several little 

 granules coalesce to form an elongated, highly refractive, 

 and clearly defined object, rapidly attaining its real size, and 

 this is the spore. The remainder of the cell-contents has now 

 disappeared, leaving the spore in a dark, very resistant mem- 

 brane or capsule, and beyond this the weak cell-wall. The 



