128 ON VAEIABILITY AND ADAPTATION 



sixteen, ten " species " were obtained, a to h. In only four of 

 the cases was the form present, even doubtfully, that described 

 by Koch (Cunningham, bacillus a). In some three different 

 comma bacilli were present at the same time. 



The forms described by Cunningham may be divided into 

 two groups. The first contains only one which does not liquefy 

 gelatine, does not show interstitial growth in agar-agar, does 

 not develop " cholera red " on the addition of acids, and morpho- 

 logically is distinguished by its large size and great variability 

 of form and curvature. This I feel inclined to consider as a 

 truly different species. The other group contains all the other 

 nine, which liquefy gelatine, are capable of interstitial growth, 

 give the " cholera red " reaction, but all show fairly permanent 

 differences in the rate of liquefaction of gelatine. In six the 

 rate is distinctly rapid, in the rest it is slow. In one growth 

 upon potato is luxuriant, in others there is rare acclimatization 

 to this medium, in others, again, acclimatization has never shown 

 itself. Here, then, one working where cholera is endemic, and 

 one who is a most capable observer, who had been with Koch 

 when he studied the disease in India, is so affected by the general 

 view that species are constant and distinct, that the only con- 

 clusion that he can draw from these facts is that " whilst denying 

 that the primary cause of cholera is represented by any species 

 of intestinal schizomycete which has yet been discovered," 

 it may be " that those whose development is favoured by the 

 existence of the choleraic condition may exert an important 

 influence on the ultimate outcome of individual cases of the 

 disease." If we accept the view that the spirillum is specific 

 I do not see any other conclusion from these observations than 

 that here is another well-marked instance of the production of 

 allied races. 



Only within the last few days news has come from St. Peters- 

 burg that the spirillum obtained from patients affected in the 

 cholera epidemic now raging presents marked differences in 

 size, etc., distinguishing it from Koch's original form; while 

 from the Institute Pasteur I hear that the microbe, isolated 

 from some of the doubtful cases in Paris, presented no greater 

 departure from type than is to be seen in many of the growths 

 obtained from indubitable cases of cholera. 



I might enter into the discussion of the relationship between 



