BACTERIA. 



21 



of a bacterium, this increases in size, or several little granules 

 coalesce to form an elongated, highly refractive, clearly denned 

 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, membrane or capsule, and 

 beyond this the weak cell-wall. The cell-wall dissolves gradu- 

 ally or stretches and allows the spore to be set free. 



Each bacterium gives rise to but one spore. It may be at 

 either end or in the middle (Fig. 5). Some rods take on a pecu- 

 liar shape at the site of the spore, making the rod look like a 

 drum-stick or spindle, clostridium (Fig. 6). 



FIG. 5. 



FIG. 6. 



Sporulation. After De Bary. 



Clostridium. 



Spore Contents. What the real contents of spores are is not 

 known. In the mother cell at the site of the spore little gran- 

 ules have been found which stain differently from the rest of 

 the cell, and these are supposed to be the beginnings, the sporo- 

 genic bodies. The most important part of the spore is its cap- 

 sule; to this it owes its resisting properties. It consists of two 

 separate layers, a thin membrane around the cell, and a firm 

 outer gelatinous envelope. 



Germination. When brought into favorable conditions, the 

 spore begins to lose its shining appearance, the outer firm mem- 



