SPORE-FORMA TION. 55 



temperatures, etc., there appears in their life-cycle the 

 stage to which we have referred as spore-formation. 

 This is the process by which the organisms are enabled 

 to enter a state in which they resist deleterious influ- 

 ences to a much higher degree than is possible for them 

 when in the growing or vegetative condition. 



In the spore, resting, or permanent state, as it is vari- 

 ously called, no evidence of life whatever is given by the 

 spores ; though as soon as the conditions which favor 

 their germination have been renewed these spores de- 

 velop again into the same kind of cells as those from 

 which they originated, and the appearances observed in 

 the vegetative or growing stage of their history are 

 repeated. 



Multiplication of spores, as such, does not occur ; they 

 possess the power of developing into individual rods of 

 the same nature as those from which they were formed, 

 but not of giving rise to a direct reproduction of spores. 



When the conditions which favor spore-formation 

 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 

 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 



