BY A. JEFFERIS TURNER, M.D., LOND. 85 



between the various bacilli is wide and patent. But among 

 the cocci, coccus r/ differs from coccus A only in the one point 

 that it has a feeble power of liquefying gelatine, while the 

 latter has no such power Again, coccus y is very close 

 to coccus [x, and it needs close observation to distinguish that 

 the former has a more luxuriant growth on agar, that its growth 

 is at fii'st whitish but very gradually attains a pink colour ; while 

 the growth of the latter is distinctly pink from the first. These 

 differences, so far as I have observed, are constant, but they are 

 slight, and of doubtful specific value. Again, among the 

 bacilli, I have lately isolated a culture which appears to exactly 

 resemble bacillus a, except that it possesses a less active power of 

 liquefying gelatine. A larger experience will probably multiply 

 the number of these closely similar varieties ; and their 

 occurrence raises a doubt as to whether they may not in some 

 cases be merely different forms of the same species, and may 

 not actually be transformed by different conditions of growth 

 from one form to the other. 



In one instance I have actually succeeded in breeding 

 two sub -varieties from a single species. In an agar culture of 

 bacillus a, I observed two different kinds of colonies — one a 

 very pale ochreous yellow, the other of an orange tint. The 

 parent agar culture had been kept through several hot months, and 

 was descended from a gelatine-plate colony. My first impression 

 was that the originally pure culture had become contaminated. 

 Microscopical examination of hanging-drop preparations showed 

 that both kinds of colony consisted of morphologically indistin- 

 guishable actively motile bacilli of the form I have described as 

 characteristic of bacillus a. From each growth I made a 

 gelatine plate, and from this again gelatine and agar cultures. 

 The gelatine growths of the two forms were absolutely 

 indistinguishable and quite characteristic ; the agar growths 

 presented the same differences of coloration that I have 

 mentioned. The difference is not a very great one, but so far it 

 breeds true, and the evidence seems conclusive tiiat the two 

 varieties have a common origin. 



