WHAT ARE BACTERIA ? 33 



line ; it is devoid of colour, and is highly refractile. The dark 

 outline of the spore is usually surrounded by a pale, soft, 

 gelatinous envelope, the substance of which may, in some 

 cases, be accumulated in rather larger quantity near the two 

 poles of the refractile body. As soon as these glistening 



Photo-micrograph of Bacillus subtilis, with well-developed free endospores. 

 Those in focus are seen to have clear centre and dark outline, x 1000. 



bodies make their appearance, degeneration of the protoplasm 

 of the bacteria in which they are found invariably follows, 

 but the period at which the death of the protoplasm actually 

 takes place varies in different cases. Where the spores are 

 small they may lie for some time embedded in the protoplasm 



4 



