SPORE FORMATION. 7 



can be demonstrated by methods which will be described, 

 the underlying principle of which is the prolonged applica- 

 tion of a powerful stain. The membrane is supposed to 

 confer on the spore its characteristic feature, namely, great 

 capacity of resistance to external influences such as heat or 

 noxious chemicals. Koch, for instance, in one series of 

 experiments, found that while the bacillus anthracis in the 

 unspored form was killed by a two minutes' exposure to 

 i per cent carbolic acid, spores of the same organism re- 

 sisted an exposure of from one to fifteen days. 



When a spore is placed in suitable surroundings for 

 growth it again assumes the original bacillary or spiral form. 

 The capsule dehisces either longitudinally, or terminally, 

 or transversely. In the last case the dehiscence may be 

 partial, and the new individual may remain for a time 

 attached by its ends to the hinged spore-case, or the dehis- 

 cence may be complete and the bacillus grow with a cap 

 at each end consisting of half the spore-case. Sometimes 

 the spore-case does not dehisce, but is simply absorbed by 

 the developing bacterium. 



It is important to note that in the bacteria spore forma- 

 tion is rarely, if ever, to be considered as a method of 

 multiplication. In at least the great majority of cases only 

 one spore is formed from one bacterium, and only one 

 bacterium in the first instance from one spore. Sporulation 

 is to be looked upon as a resting stage of a bacterium, and 

 is to be contrasted with the stage when active multiplication 

 takes place. The latter is usually referred to as the vegeta- 

 tive stage of the bacterium. Regarding the signification of 

 spore formation in bacteria there has been some difference 

 of opinion. According to one view it may be regarded as 

 representing the highest stage in the vital activity of a 

 bacterium. There is thus an alternation between the 

 vegetative and spore stage, the occurrence of the latter being 

 necessary to the maintenance of the species in its greatest 

 vitality. Such a rejuvenescence, as it were, through 

 sporulation, is known in many algae. In support of this 

 view there are certain facts. In many cases, for instance, 



