CLASSIFICATION OF ANAEROBIC BACTERIA 529 



positive pathogen are so similar in many respects to B. Welchii 

 that they might easily be identified as one species by many 

 workers, and it is evident that only an artificial classification 

 would separate them, yet B. egens and the other pathogens have 

 not been shown to produce spores. Asporogenous anaerobic 

 rods have not been frequently reported, but when one remembers 

 that the preliminary step in isolating anaerobes is usually a 

 heating process, it will be clear that the proportion of anaerobes 

 that do not sporulate may be considerably greater than one 

 would estimate on the basis of published descriptions. The 

 soil mixtures from which Weinberg's organisms, B. egens of 

 Stoddard, and my above-mentioned pathogen were isolated had 

 all been subjected to a physiological weeding out in human tissue 

 before they were inoculated into media, and a colony method 

 without heating was thus practicable for isolation purposes. 



The matter of a primary division of the rod-shaped bacteria 

 then simmers down to a question of whether an anaerobic habit 

 or a spore-forming habit is the more fundamental one. It is 

 perfectly evident that certain asporogenous anaerobes have 

 closer physiological affinities with certain sporulating anaerobes 

 than the latter have with the sporulating aerobes or even with 

 most other anaerobes. We may have in the power of sporulation 

 such a phenomenon as that noted among the insects: there are 

 primitively wingless insects, the Thysanura, and there are vari- 

 ous types of insects, such as the Siphon apter a, and the Mallo- 

 phaga, which have lost their wings, and there are insects that 

 have no wings at the time or in the form that we happen to 

 observe them — larvae and pupae and worker ants and apterous 

 mutants of winged forms. Therefore the possession of wings, 

 conspicuous insect characteristic that it is, has been discarded 

 as a character for the separation of insects from other forms. 

 The whole question is reduced to the much agitated one: Are 

 we going to give precedence to physiological or to morphological 

 characters in the classification of the bacteria? 



Morphology of the sporangium has been used as a character by 

 a long succession of workers. Its use may be more vigofously 

 attacked than that of the other characters. It was introduced 



