SPORE-FORMA TION. '59 



present, the protoplasm of the vegetative cells is seen 

 to undergo a change. It loses its normal homogeneous 

 appearance and becomes marked by granular, refractive 

 points of irregular shape and size. These eventually 

 coalesce, leaving the remainder of the cell clear and 

 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 



FIG. 6. 

 f *+*?* 



V 



V 



\ 



a bed 



a. Bacillus subtilis with spores, b. Bacillus anthracis with spores, c. Clos- 

 tridium form with spores, d. Bacillus of tetanus with end spores. 



of a cell-membrane and a transparent, clear space 

 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. When 

 thus perfectly developed, the spore may be regarded as 

 analogous to the seeds of higher plants. Like the seed, 

 it evinces no evidence of life until placed under condi- 

 tions favorable to germination, when there develops 

 from it a cell identical in all respects with that from 

 which it originated. Its tenacity of life, as in the case 

 of seeds, is almost unlimited. It may be kept in a dry 

 state, and this has actually been done, for years without 

 losing the power of germination. The glistening, en- 

 veloping spore-membrane is not of uniform thickness 



