SPORES 



27 



-Endospore 



these cells, however, is very small. Many bacteria, therefore, inter- 

 rupt their growth and multiplication by entering into a resting 

 condition, in which no growth or multi- 

 plication takes place until favourable cir- 

 cumstances once more arise. Any portion 

 of a bacterial cell which is separated 

 from the rest for this purpose is called 

 a Spore} If this portion is formed inside 

 the cell it is called an endospme (Fig. 41). 

 The formation of endospores is very 

 common in the Bacteriaceae, is found 

 only in two species in the Coccaceae, 

 and never in the Spirillaceae, nor in 

 any of the higher bacteria (Chlamydobacteriaceae) so far as is at 

 present known. 



The endospores are thick-walled glistening structures of an oval or 

 round shape. Each contains dense protoplasm and reserve materials, 

 so much so that the proportion of water is less than in the ordinary 

 bacterial cell. 



Development of the Endospore. The essential part in the develop- 

 ment of an endospore consists in a concentration of the protoplasm into 



a certain area, this area being 



Bacillus in which an endo- 

 spore has formed. 



% 



r'k 



:■■>) 



d 



^0 



Fig. 42. — Stages in development nf endospore. 



then surrounded by a tough 

 membrane. The rest of the bac- 

 terial cell usually disappears and 

 the endospore is liberated. The 

 first stage in this development is 

 shown in Fig. 42ffl. The area into 

 which the protoplasm condenses 

 is visible by careful staining as a 

 circular or oval area, which stains 

 less deeply than the surrounding 

 protoplasm. Some observers claim 

 to have found inside this vacuole, 

 as the area is called, a nucleus 



surrounded by a thin film of protoplasm, which is connected with the 



' De Bary divided bacteria into two kinds, those capable of forming endospores, 

 and those incapable of doing so. In the latter case it was assumed that the 

 veg^ative cells themselves put on a thicker membrane and became resistant 

 cells. In this condition they were called arthrospore.s. It was supposed that 

 they afterwards germinated, but this has never been demonstrated. 



