1216 



and its conditions for nntrition in the poljphagous state, it is quite 

 sure that these two bacteria are nearly allied. Consequently tve 

 must conclude that the nitrate ferment can feed on the same organic 

 substances, which B. oUgocarho plains finds at its disposal, as well in 

 the liquid as in the extracted agar and the silica plates. That those 

 substances are at least partly provided by the atmosphere of the 

 laboratory, I have pointed out in the above mentioned paper. 



The nature ot these substances is not yet stated, but it is very 

 probable that volatile products, given off by other bacterial cultures 

 occur among them. 



In this relation I call to mind the experiment mentioned above 

 with paraftin oil, whose presence does not stop the nitratation. Perhaps 

 the nitrate ferment can feed on it, or on allied substances, whose 

 occurrence in the soil or the atmosphere seems not excluded. 



From the foregoing must be concluded, that chemosynthesis for 

 the nitrate ferment is unproved and that, as far as can be judged 

 at present, it is in this case a quite superfluous hypothesis. 



Summarising we find, that the nitrate ferment represents a definite 

 state of a greater unity, a physiological species, which may be kept 

 constant in the nearly pure anorganic nitrite solutions, but which, at 

 better nutrition with organic substances, passes into an other state 

 of that unity, another physiological species much more constant. 



If the former, that is the nitratating state of the ferment, is called 

 Nitrihacillus oUgotrophm, the latter, r.on nitratating coTidition, maybe 

 named Isl itribaciUus pohjtrophus. The conversion of the former into 

 the latter, that is in the direction 



N. oUgotrophus — ^ N. polytrophus 

 easily takes place ; the passage in opposite direction : K. polytrophus -^ 

 N. oUgotrophus, cannot be effected by the usual laboratory experiments. 



Although the nutrition of Xitrlbacillus oUgotrophus requires an 

 almost total absence of organic food, there is no cause to ascribe to 

 this ferment the faculty of chemosynthesis. 



The question, where the here described case of the formation of 

 a physiological species must be placed in the system of biology, is 

 to be answered as follows. 



It cannot be an example of mutation, such as I have amply 

 described for a number of microbes, as the more or less constant 

 products of the mutation process arise at the side of the stock, and 

 continue to exist with it under the most different conditions. 



But it is a new case of hereditary modijication, in fact not much 



