SELECTED PAPERS 



In summarizing the above it is tempting to conclude that on the one 

 hand phylogeny has led to the origin of various morphological groups, 

 whilst, on the other hand, an evolution in metabolic properties has 

 occurred which together are responsible for the almost unlimited 

 diversity of bacterial species. Before attempting to apply these prin- 

 ciples in the construction of a system, we will first critically examine 

 the more recent contributions to the classification of bacteria. 



3. CRITICAL EXAMINATION OF RECENT CONTRIBUTIONS 

 TO THE CLASSIFICATION OF BACTERIA 



The large number of papers in which ideas on bacterial taxonomy are 

 advanced makes an endeavour to give a moderately complete survey 

 altogether impossible. Therefore we shall confine ourselves to a con- 

 sideration of the more strictly taxonomic publications. 



The system of Lehmann and Neumann [1926], adapted to modern 

 needs since its inception in 1896, may still lay claim to a serious con- 

 sideration. The outstanding feature, and at the same time the weak- 

 ness of the system, is undoubtedly its simplicity. Although for the 

 separation of the families of the Schizomycetales morphological char- 

 acters are used exclusively, it would seem that a far better use could 

 be made of such characters to express natural relationships. In this case 

 the Desmobacteriaceae, which have nothing in common with the other 

 five families, would have been set aside as a group equivalent to the 

 orders of Schizomycetales and Actinomycetales. The same holds for the 

 family of the Spirochaetaceae. The remaining four families seem at first 

 sight acceptable as units resulting from a gross subdivision. Yet it 

 appears from a closer inspection of the accepted genera that their 

 grouping violates the principle of natural relationship in many respects. 

 Thus one finds in the large, physiologically very heterogeneous, genus 

 Bacterium organisms with polar flagella which are much more closely 

 related to the family Spirillaceae than to the greater part of the 01 her 

 Bacterium species. Furthermore, the unmistakable relations! dp be- 

 tween the species of the genus Plocamo bacterium with those of the Pro- 

 actinomycetaceae is fully neglected, even to the extent of incorporating 

 them in different orders. As regards the family of the Desmobacteriaceae 

 its extremely heterogeneous nature should be emphasized. Apart 

 from the fact that Lehmann and Neumann apologetically incorporate 



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