954 Transactions of the Society. 



are remarkably regular, their height being usually nearly equal to 

 their breadth ; they attain a considerable length, often comprising 

 20 or 80 sj^irals or more. 



I must here remark that the term " comma bacillus," though 

 so well known that it would be superfluous to object to its use, is 

 not even in a popular sense correct, the microbe is not a Bacillus 

 in Cohn's definition of that genus,* which is one consisting of 

 •' straight filaments," nor is it in the usual acceptance of the term 

 comma-shaped, the cells being uniformly cylindrical throughout. 

 It has, however, been overlooked hitherto, that the term " comma " 

 as applied to Spirilla, was first employed by Dr. Cossar Ewart and 

 Mr. Patrick Geddes, in their account of the life-history oi Spirillum ;t 

 the forms, however, which they figure are much more comma-like 

 than any I have observed the cholera microbe to assume. This 

 arises from the circumstance, that in their figures the first coil or 

 turn of the spiral seems to commence near one extremity of the 

 cell, whereas in Koch's microbe it occurs, to my observation, almost 

 invariably about the centre. 



In all stages of development it is motile, more actively so in 

 the later than the earlier forms. It possesses a large and very 

 distinct flagellum, as first stated by Mr. Nelson ; this appendage 

 or organ is relatively larger and more conspicuous than in any other 

 schizophyte I have hitherto seen. It often occurs at both ends of 

 the cell, and frequently forms a loop, which may be readily mistaken 

 for a corpuscle or vesicle attached to the cell ; this appearance is 

 seen in some of Koch's photographs of septic bacteria. J How 

 conspicuous the flagellum here is may be judged of by the fact that 

 I have in some cases been able to draw it without difficulty through 

 the camera lucida, as in the sketch here shown. On a future 

 occasion I hope I may be able to demonstrate these flagella under 

 the Microscope ; to do so requires some care and deliberation, but it 

 is a subject of interest from more points of view than one, to the 

 microscopist. 



The plasma of the unstained cell, in all stages of development, 

 is usually homogeneous, but in preparations stained not too deeply, 

 the ends are often seen to be more coloured than the central portion, 

 as originally described by Koch. 



Its methods of multiplication are in some respects obscure; 

 usually this occurs by transverse fission, as is characteristic of this 

 group of the lower fungi, and takes place largely in an early stage 

 of development long before the mature Spirillum-hvm is attained. 

 Dr. Klein, however, has observed and described another method of 

 development, by longitudinal fission, in which the short curved 



* Beitr. Biol. Pflanzen, Bd. i. H. ii. p. 173. 



t Proc. Roy. Soc, xxvii. (1878) p. 484. 



X Beitr. Biol. Pflanzen, Bd. ii. PI. xi. fig. 5. 



