14 A MANUAL OF BACTERIOLOGY 



Reproduction by spore formation is met with in some 

 species, and is generally described as being of two kinds. 

 In the first, " endogenous " spore formation, a bright 

 refractile round or ovoid body is formed within the bacterial 

 cell, the development of which can be watched under the 

 microscope. Rowland describes the process of spore 

 formation as follows : Refractile, oily-looking droplets, 

 which do not stain with roseine, appear and ultimately 

 coalesce, forming the spore. The cell-plasma at the same 

 time diminishes and retracts from the cell-membrane. 

 The roseine-staining granules increase in number and 

 aggregate into two spherical masses, which dispose them- 

 selves one at each end of the cell. The cell-membrane 

 collapses somewhat, and, when the spore is fully formed, 

 ruptures transversely, leaving two cup-shaped receptacles, 

 in which the granules and remains of the plasma are still 

 recognisable. Only one spore develops in each cell, and 

 the spores serve to perpetuate the race when it is threatened 

 with extinction from adverse circumstances. Each spore 

 consists of a little mass of protoplasm enclosed within a 

 very tough and resisting membrane, which tends to pre- 

 serve its vitality even under unfavourable conditions ; 

 for spores resist the action of desiccation and germicidal 

 agents to a much greater degree than the fully developed 

 organisms. Spores vary much in size and in the position 

 they occupy within the bacterial cell in the different 

 species ; their diameter is usually about the same as that 

 of the cell in which they are developed, but may be much 

 greater, and in position they may be central or terminal, 

 and sometimes the spore -bearing cells are swollen or 

 club-shaped ; these are termed " clostridia." Endospores 

 are still unknown in a large number of species. The 

 second variety of sporulation, " arthrospore " formation, 

 is of doubtful occurrence, but is stated to take place as 

 follows : Some of the elements formed by fission are 



