CONTRIBUTIONS TO THE CYTOr.OaV OF THE BACTEIUA. 457 



material. In addition to tliese, pale vacuoles are usually to 

 be seen. They may be irregularly scattered through the cyto- 

 plasm (b, c) or arranged in a single line down the middle of 

 the organism (a). In the latter case the refractive bodies 

 frequently occur in pairs between the vacuoles — as shown in 

 fig". A. Intra-vitam staining^ brings out the refractive 

 bodies very sharply, but does not reveal the nucleus. 



Multiplication can be easily observed under the microscope. 

 It is accomplished by the rods undergoing a transverse fission 

 in a manner which closely resembles that of many Bacteria. 

 If long cells be carefully scrutinised, some of them can be 

 found which show faint indications of a septum towards the 

 middle of the organism. The septum makes its first appear- 

 ance as two faint transverse lines, extending towards one 

 another from opposite sides, in the centre of the cell. A little 

 later the lines appear to meet, so that a delicate septum 

 extends right across the middle of the cell (see Text-fig. c 

 — middle individual). The septum becomes thicker, and cuts 

 the parent cell into two equal daughter-cells. After separa- 

 tion — which noAv takes place — the contiguous ends of the 

 daughter-cells are square, but they rapidly assume a rounded 

 appearance (cf. text-fig. d). The whole process of division 

 — as seen under the microscope — takes several hours, pro- 

 ceeding very slowly. I have not been able to follow the 

 division of the nucleus satisfactorily in the living oi-gauisms. 



All the material upon which these observations are based 

 came from the large intestine of a single B. constrictor 

 which had been in captivity for some time. I have, therefore, 

 no data to indicate the frequency with which the parasite 

 occurs in this snake. 



On examining the contents of the large intestine of the 

 snake, soon after death, I found a large number of organisms 

 present in the stages which I have just described. My first 

 conclusion — not unnaturally — was that I was dealing with a 

 large species of Bacterium. Had I not made further 

 observations upon the subsequent development of the organ- 

 ' With neutral red, methylene blue or BrillantcresyDilaii. 



