1217 



differing from the loss of virulence of many pathogenic bacteria, 

 only much more evident as to the outward characteristics. Comparable 

 to, but not identic, with the pleomorphy of many Fungi ; — com- 

 parable, too, to the differentiating process in the ontogenetic 

 development of the higher plants and animals, the result of which 

 we observe in the various cell-forms of one and the same indi- 

 vidual. By artificial nutrition, and 'independently of their relation 

 with the other cells, some of these cells can multiply without change 

 of properties, hence, also without returning to the state of the 

 mother-cell or the embryonal cell from which they sprung. The 

 increase of connective tissue and of the muscle cells of the embryonal 

 heart, cultivated in bloodplasm, are good examples. 



Finally I wish to remark that the physiological formation of 

 species is not an isolated case for the nitrate ferment, but that it 

 same takes place in the life history of many microbes of soil and 

 water. To these other species, showing the same disposition, 

 belongs B. oUgocarhophihL% which is, as said, nearly allied to the 

 nitrate ferment itself and on some media cannot even be distinguished 

 from it. 



By the isolation of this bacterium on nitrite- or nitrate agar with- 

 out organic food, the floating films of crude nitratations, colonies 

 are obtained, which by their white, dry surface are perfectly like 

 the films of the culture liquids, and which, when repeatedly 

 transferred on the same medium, without other organic food, can 

 preserve the film-character unchanged in the course of years. But 

 if these cultures are transferred to broth- or peptone agar, their 

 characteristic appearance gets lost, wet and glittering colonies 

 arise, semi-spherical, not extending sideways and seemingly belonging 

 to quite another species. When multiplying they, hereditarily transmit 

 their newly acquired properties, also ivhen again transplanted on 

 media without organic food. 



The thus obtained polytrophic form and the oligotrophic mother- 

 form, make a couple, quite comparable to the two conditions of the 

 nitrate ferment. 



For a long time I considered the polytrophic form of B. oligo- 

 carbophilus as a wholly different species, always mixed with the 

 primitive stock as an impurity. Erroneously I thought, that the 

 isolation could only be effected by means of a better nutrition, the 

 oligotrophic form thereby dying off. So, I had fallen into the same 

 error as my predecessors concerning the nitrate ferment, but the 

 recognition of the physiological formation of species now brings the 

 required light. 



(May 29, 1914.) 



