COXTRIBUTIOXS TO THE CYTOLOGY OF THE BACTERIA. 427 



On account of its very large size. B. f lexilis is particularly 

 •well suited for observations upon its structure. I will now 

 desci-ibe the appearances which it presents when fixed by a 

 good wet method and stained by a good cytological stain. 



I have given two figures of organisms so treated (PI. 18, 

 figs. 119, 120). Fixation, sublimate-alcohol (Schaudinn) ; 

 stain, Heideuhain's iron-hajmatoxylin. It may be noted here 

 that alihougli this method gives good results on the whole, it 

 is very difficult to obtain uniformly sharp differentiation. 

 Different individuals behave differently towards the stain, so 

 that in the same preparation well-stained, over-stained and 

 «ndei"-stained organisms are often found side by side. 



When examined under the highest magnification which I 

 have been able to use (Zeiss 2 mm. apochromatic oil- 

 immersion, compensating ocular 18) the following internal 

 structure can be made out. The cytoplasm appears homo- 

 geneous and very finely granular (as it does in life) or else 

 shows a rather indistinct alveolar arrangement (cf. fig. 120). 

 The very well-marked cytoplasmic alveoli described by 

 Schaudinn (1902) in B. biitschlii are very much more 

 distinct than anything I have ever seen in B. flexilis. In 

 the latter the cytoplasm is, at most, slightly alveolar. A 

 number of round black granules can be seen scattered 

 through each cell (figs. 119, 120). They are usually more 

 numerous towards the periphery than in the centre. These 

 granules constitute — I believe — the nucleus, and are probably 

 -composed largely of chromatin. Their behaviour during 

 spore-formation I have already described (Dobell, 1908). No 

 other structures are to be seen. 



I believe that the figures (figs. 119, 120) give a faithful 

 picture of the structure of B. flexilis. I am convinced that 

 were other structures present — e. g. a vesicular nucleus, or a 

 nuclear filament — they would have been visible in some of my 

 preparations. I conclude, therefore, that the internal structure 

 of B. flexilis consists simply of a faintly alveolar cytoplasm 

 in which small granules of chromatin are imbedded. 



Having said so much about B. flexilis itself, I Avill now 



VOL. 56, PAET 3. NEW SERIES. 30 



