PROSPECTS FOR A NATURAL SYSTEM OF CLASSIFICATION OF BACTERIA 



unmistakable morphological affinities with the Cyanophyceae that in 

 our opinion they must be considered as colourless derivatives of the 

 genera Oscillatoria, Phormidium and Schizothrix (see also Pringsheim I.e.). 



As for the Spirochae tales and the Myxobacteriales they form well-defined 

 groups whose affinities with the Eubacteriales are at least doubtful. 

 Therefore they may well be ignored here. On the other hand the re- 

 lationship of the Actinomycetes to the Eubacteriales is very clear; as is 

 generally accepted they represent stages of higher development of the 

 Mycobacterieae. At the same time they form such a special and extensive 

 group by themselves that their classification falls outside the scope of 

 this study. 



The remaining order of the Chlamydobacteriales cannot so easily be 

 disposed of. At first sight the representatives of genera like Leptothrix, 

 Crenothrix and Sphaerotilus do not seem at all related to any of the Eu- 

 bacteriales. Although we cannot yet express any definite opinion regard- 

 ing the taxonomy of this group it appears probable that it is very 

 heterogeneous and that it harbours organisms (Crenothrixl) which are 

 closely related or belong to the Eumycetes, as well as organisms which, 

 like Sphaerotilus natans, are related to sheath-free filamentous Eubacte- 

 riales (Bacillus, Mycobacterium and Thermo bacterium species). In this 

 respect it is tempting to draw the attention on the one hand to such 

 organisms as Leptothrix hyalina (Migula) Bergey et al. and Sphaerotilus 

 paludosus Smit [Smit, 1934] which, although they are usually reckoned 

 to belong to the Chlamydobacteriales, are reported to lack a sheath, and 

 on the other hand to a bacterium, like Bacillus fwiicularius, which, al- 

 though a true Bacillus species, forms a distinct sheath under special 

 nutritional conditions [Kluyver and Van Niel, 1926]. Moreover, the 

 latter phenomenon is also frequently encountered in the group of the 

 true lactic acid bacteria [Orla-Jensen, 1919]. 



Table II gives a survey of the families, tribes and genera of the order 

 Eubacteriales. After all that has already been said this table will not 

 need any further comment. 



In concluding we wish to make the following remarks. 



As has been amply set forth in the discussion of the general prin- 

 ciples of classification it is necessary both from a scientific and from a 

 practical standpoint to aim at a system which is worthy of the design- 

 ation 'natural'. We fully realize that the result of our own classifica- 

 tory attempt has only very imperfectly approximated this goal. 



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