ENDOSPORES 



25 



accumulation, within this area, of the nuclear material of which the spore is 

 formed. Meyer and his supporters lay great stress on the appearances seen during 

 sporulation, as evidence for the existence of differentiated nuclei. Those who 

 have studied the internal structure of bacterial cells have, for the most part, in- 

 cluded the process of spore-formation in their observations, and the papers which 

 have already been referred to contain full discussions of this question. 



The situation of the spore within the bacterial cell, which may be terminal, 

 subterminal, or approximately equatorial, gives a distinctive morphology to many 

 bacterial species. In addition, the diameter of the ripe spore is often greater than 

 that of the bacillus which contains it ; so that the cell is distorted and, according 

 to the position of the spore, " drum-stick," " barrel," or other irregular forms 

 may be presented (Fig. 6). 



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Fig. 7. — Germination of spores by equatorial rupture. 

 An unidentified soil bacillus. B. B. mesentericus ( X 4,660). 

 (From photographs kindly supplied by Dr. C. F. Robinow.) 







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The germination of a spore, when placed under favourable conditions, may 

 occur by simple enlargement of the spore without obvious rupture or shedding 

 of the spore-envelope, though this is an unusual method. Far more frequently 

 the spore-envelope ruptures, either at one pole or equatorially, and the spore as 

 it develops into a bacillus sheds its enveloping membrane (Figs. 6 and 7). 



By careful staining of mildly hydrolysed preparations of spores, Robinow 

 (1942) was able to distinguish three structures takinji part in the germination of 

 spores of B. mycoides and other members of 

 the Bacillus group. In the resting spore 

 there was a delicate membrane, containing 

 an apparently structureless rod of cytoplasm 

 and a small, sometimes dumbbell-shaped, 

 chromatinic body attached to, but distinct 

 from, the rod (Fig. 8). With germination, 

 the chromatinic bodies are transformed into 

 ring-shaped bodies, which enter the cyto- 

 plasmic rod, and merge with the cytoplasm. 

 At a later stage of germination the chromatinic 

 bodies reappear and differentiate into the llBif* '^' J 



dumbbell forms characteristic of the vege- Yiq. 8. — Resting spores of /:;. miicoides 

 tative form. Robinow (personal communi- (:;4.()()0). 



cation) also distinguishes a layer of refractile <^^°'" ^ PD^e'^'Fl' rSw.?'''"'^ "^ 



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