14 THE BIOLOGY OF BACTERIA 



hours. The spores may be situated in the middle of the bacillus 

 (as in B. anthracis, B. acidi lutyrici, etc.), towards one end (Bacillus 

 of Malignant (Edema), or actually terminal (B. tetani). Those spores 

 produced inside the capsule of the bacillus are termed endospores. 

 Hueppe has described the spores of certain streptococci as arthrospores. 

 The spores of yeast are termed ascospores. The spores of all 

 bacillary species possess, however, certain characters in common. 

 They are as follow. The spore is generally oval, though more 

 spherical in the Hyphomycetes : it is bright and glistening in aspect ; 

 it is often greater in diameter than the bacillus giving rise to it ; 

 its capsule is thicker and stronger than the capsule of the parent 

 bacillus; and it is generally held that the contained protoplasm is 

 more concentrated, so to speak, than that of the bacillus. These two 

 last characters are of chief importance to us, for it is owing to them 

 that spores possess such marked power of resistance. Cohn has 

 suggested that the capsule of a spore is in reality a double envelope, 

 an inner one of fatty and an outer one of gelatinous nature, and it is 

 owing to this that its resistance to heat and dessication is due. The 

 protoplasm of the spore contains, of course, the essential constituents 

 of the mother cell. It is the method by which "the continuity of 

 germ plasm " is secured in these lowly forms of life. Under favourable 

 circumstances this spore-protoplasm will germinate into a new bacillus. 

 It should be understood that whilst holding the view that 

 spores are a resting stage during adverse conditions,* we fully 

 recognise that certain favouring external conditions are essential 



* Yeast can be effectually starved by cultivating on a small block of plaster- 

 of-Paris kept moist under a bell jar ; under these circumstances the yeast is 

 supplied with nothing but water. In a few days the protoplasm of yeast cells thus 

 circumstanced becomes filled with vacuoles and fat cells. The protoplasm has 

 been undergoing destructive metabolism, and, there being nothing to supply new 

 material, has diminished in quantity and at the same time been partly converted 

 into fat. Both in plants and animals fatty degeneration is a more or less constant 

 phenomenon of starvation, and to this bacteria are no exception. After a time the 

 protoplasm collects towards the centre of the cell, and divides simultaneously into 

 four masses arranged like a pyramid of four billiard balls, three at the base and 

 one above. These are the ascospores, and sooner or later they are liberated by 

 the rupture of the mother-cell wall. Certain of the Streptothrix family also 

 " sporulate " when they find themselves, like yeast upon gypsum, surrounded 

 by an unfavourable environment. Again, in old cultures, it will be found that 

 when the food supply has been exhausted the bacteria have either sporulated or 

 have died. For these reasons sporulation may be looked upon not as a method 

 of multiplication but one of reproduction, of carrying on the species under adverse 

 conditions. With regard to the rapid formation of spores under apparently 

 favourable circumstances (B. filamentosus^ B. anthracis, etc. ), it must be borne in 

 mind that the medium may not be by any means so favourable as appears to be the 

 case (Flugge). It is clear that the food supply immediately around many of the 

 bacteria in a culture must soon be exhausted. Besides, there is the toxic influence 

 early at work, often as an inimical agency acting unfavourably towards the bacillus 

 producing it. So that the appearance of spores in such a culture may still be due 

 to conditions which are actually unfavourable. 



