151 



DESKOWITZ i) have again forwarded important arguments in favour 

 of the view that microbial variation is indeed largely due to gene 

 mutation, and the same holds also for MAYER 2 ), to whose up to date 

 survey of the problem in question the reader may be referred. 



There is, however, still another contribution of BEIJERINCK to our 

 knowledge of the variation problem which may not pass unmentioned. 

 In 1914 BEIJERINCK published a paper which bore the title: "On the 

 nitrate ferment and on the physiological formation of species" 3 ). He 

 reported in this paper his experiences, undoubtedly collected over 

 numerous years, regarding the nitrate ferment. On the whole his 

 observations are in substantial agreement with the results of WINO- 

 GRADSKY'S classical study which appeared as long back as 1890. 

 However, BEIJERINCK added one new feature to the picture drawn 

 by the Russian scientist. He gave it as his conviction that, contrary 

 to the current opinion, the nitrate ferment was quite capable of pro- 

 liferation in common media rich in organic substances. But on doing 

 so, its ability to oxidize nitrites was irreparably lost. Out of the oligo- 

 trophic nitrate ferment, Nitrobacter oligotrophum, a new species, Ni- 

 trobacter polytrophum, was irreversibily formed, hence the term "phy- 

 siological formation of species". It will be clear that it is extremely 

 difficult to arrive at a final decision regarding the correctness of this 

 theory. For the irreversibility of the assumed conversion makes it 

 almost impossible to disprove that the so-called polytrophic form is 

 not actually a common heterotrophic contaminant which has main- 

 tained itself in the cultures of the nitrate ferment during its cultiva- 

 tion in the inorganic media. 



It is, therefore, not surprizing that WINOGRADSKY has severely 

 criticized BEIJERINCK'S observations and in consequence has fully 

 rejected his theory of physiological species formation 4 ). It may be 

 added that the results of the recent investigations of KINGMA BOLTJES 

 are also against BEIJERINCK'S ideas 5 ). 



Yet, it seems wise not to lose sight of the fact that the more or less 

 startling observations in question were made by a BEIJERINCK in the 

 last phase of his career, that is to say by a microbiologist who was not 

 likely to be led astray by common contaminants. Moreover, again 

 according to BEIJERINCK, this example of physiological species for- 

 mation did not stand alone. In the last paper which he published 

 before his retirement from the chair, BEIJERINCK described a similar 

 phenomenon for the bacterium active in the process of denitrification 

 with sulphur as a source of energy 6 ) . On transference into organic 



1) M. W. DESKOWITZ, Journ. of Bact. 33, 349, 1937. 



2) H. D. MAYER, Das Tibi-Konsortium, nebst einem Beitrag zur Kenntnis der Bak 

 terien-Dissoziation. Delft, 1938. 



J) Folia Microbiologica 3, 91, 1914. 



) Compt. rend, de 1'Acad. d. Sc. 175, 301, 1922. 



5) T. Y. KINGMA BOLTJES, Archiv f. Mikrobiol. 6, 79, 1935. 



6) Proc. Kon. Akad. v. Wet. Amsterdam 22, 899, 1920. 



