SPOBE-FORMATION. 43 



completed, in an indentation of the adjacent extrem- 

 ities of the young segments, so that by the aid of 

 high magnifying powers these surfaces are seen to be 

 actually concave. Bacilli never divide longitudinally. 



With the spore-forming bacilli, under favorable con- 

 ditions of nutrition and temperature, the same is seen 

 to occur during vegetation ; but as soon as these condi- 

 tions become altered by the exhaustion of nutrition, 

 the presence of detrimental substances, unfavorable 

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

 cycle to which we have referred as " spore-formation." 

 This is the process by which the organisms are enal)led 

 to enter a stage 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 stage, as it is 

 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 cliange. 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 



