34 THE FUNDAMENTAL PRINCIPLES. 



their body of certain dyes which have great affinity for the 

 protoplasm of ordinary bacteria, so that a special method 

 must be adopted for their staining, as will be described 

 later. 



Spores therefore preserve the species, when these would be 

 destroyed if dependent solely on the bacilli for their preser- 

 vation. 



2. The Arthrospore. 



The foregoing spore-formation, known as endospores, is the 

 usual mode of spore-formation found in bacteria, and is lim- 

 ited to the rod and spirilla forms ; but another form of 

 spore, called arthrospore, is mentioned by some as occurring 

 occasionally in the round or cocci forms. This consists in a 

 special jointed projection forming from the outside of the 

 cells, and capable later of developing into the original cell. 

 This form of spore-formation is generally doubted at the present 

 time. 



Spores are incapable of producing other spores, and can, only 

 when placed in suitable conditions, develop into the type of 

 bacilli which gave them birth. When this occurs the spore 

 begins to elongate, loses its glistening appearance, and finally 

 its membrane ruptures at one end or in the centre and gives 

 exit to a fully developed bacillus. 



Spores may be distinguished from rounded bacteria by 

 means of their brighter, more glistening appearance, their 

 power of resisting stains, and the fact that in suitable media 

 they develop into bacilli. 



Significance of Sporulation. Whether the original idea that 

 spores form, in bacteria capable of producing them, only 

 when the latter are submitted to external noxious influences, 

 and for the purpose of perpetuating the species, or whether, 

 as more recently maintained, sporulation is the result of the 

 highest expression of the complete development of bacteria, 

 is not at present fully determined, though the dictum of 

 authorities inclines to the latter view, and the spore-formation 

 of some of the best-known and studied bacteria, as anthrax, 

 seems to lend color to this theory. 



