44 SA CTEBIOL OGY. 



transparent. When this coalescence of highly refrac- 

 tive particles is complete the spore is perfected. In 

 appearance the spore is oval or round, and very highly 

 refractive — glistening. It is easily differentiated from 

 the remainder of the cell, which now consists only 

 of a cell-membrane and a transparent, clear fluid 

 which surrounds the spore. Eventually both the cell- 

 membrane and its fluid contents disappear, leaving the 

 oval spore free; it then gives the impression of being 

 surrounded by a dark, sharply defined border. It 

 evinces no motion other than the mechanical tremor 

 common to all insoluble microscopic particles suspended 

 in fluids, and it remains quiescent until there appear con- 

 ditions favorable to its subsequent development into a 

 vegetative form similar to that from which it originated. 

 Occasionally the membrane of the vegetative cell in 

 which the spore is formed does not disappear from 

 around it, and the spore may then be seen lying in a 

 very delicate tubular envelope. Now and then, rem- 

 nants of the envelope may be noticed adhering to a 

 spore which has not yet become completely free. 



In staining, the spore-containing cells do not take 

 up the dyes in a homogeneous way. By the ordinary 

 methods the spores do not stain, so that they appear in 

 tlie stained cells as pale, transparent, oval bodies, sur- 

 rounded by the remainder of the cell, which has taken 

 up tlie staining. 



A single cell produces but one spore. This may be 

 located either at an extremity or in the centre of the 

 cell. (Fig. 4.) 



Occasionally spore-formation is accompanied by an 

 enlargement of the cell at the })oint at which the pro- 

 cess is in progress. As a result, the outline of the cell 



