ROGER G. PERKINS 133 



backward is an open question, and in the meantime we find in general that, at least 

 under ordinary conditions, in the laboratory of nature rather than in that of the 

 specialized scientist, the coccus remains coccus. There are two qualifications to the 

 acceptance of a single group for all spherical forms. Some desire to place the so-called 

 ''primitive" nitro group together, both the spheres and the rods, on the basis of sim- 

 ilar physiological characters regardless of form. In a similar manner there are those 

 who believe that organisms of the lactococcus type should be placed with those of the 

 lactobacillus type. In the first report of the Society of American Bacteriologists Com- 

 mittee in 191 7, Lactobacillaceae was recorded as a family, and in the final report it 

 was placed as a tribe under Baderiaceae. 



Further subdivisions of the family have been made in various ways. Winslow, 

 Bergey, Castellani and Chalmers among recent workers made a primary division on 

 the basis of parasitism, following this by morphology. The Society of American Bac- 

 teriologists follows Winslow closely, but many writers feel that the establishment of 

 habitat, or its subdivision parasitism, is likely to be misleading and does not produce 

 natural groups. 



Hucker {loc. cit.) considers pigment as a species rather than a generic distinction, 

 and sees no reason for the retention of the red pigment formers as a genus among thp 

 cocci, the rest having already been generally abandoned in this group. In general, all 

 the chemical and physiological characters are best used in the differentiation of 

 species and varieties. 



Rod forms. — There remains the large group of rod forms about whose classifica- 

 tion there is a more or less consistent disagreement. As will be noted by the chart, 

 the tendency of foreign writers is to group all of these under one head, sometimes with 

 one name, sometimes with another, though Orla- Jensen has made much wider sepa- 

 rations, from which one of the American expansions has come. This is the group of 

 supposedly "primitive" organisms, mentioned in this paper as the "nitro"- forms, 

 accepted with more or less modification by Buchanan, the Committee, and Bergey and 

 criticized by others, as noted earlier in the paper. An additional family, the Pseudo- 

 monadaceae, including pyocyaneus and allied forms, is found as such only in the 

 Society of American Bacteriologists and in Breed's comments (1917), elsewhere hav- 

 ing a maximum rank of genus. Another American expansion is the elevation to fami- 

 ly rank of both the spore-formers and the non-spore-formers, as Baderiaceae and Ba- 

 cillaccae, a proper division, though there is argument as to the rank which should be 

 given these groups. Buchanan and Castellani, in agreement with most of the Euro- 

 pean authors, prefer subfamily rank. The variety of further divisions is unending, 

 and, as noted earlier, far more work has been done on species and variety than on 

 genus and higher ranks. It is almost impossible to summarize within any reasonable 

 space the variety of opinions. Primary difi"erentiations, after or before relation to 

 spore formation, are made on the basis of pigment formation, habitat, morphology, 

 and physiology. Bergey, in his eleven tribes of non-spore-formers, names two on the 

 basis of pigment formation, three on parasitism, five on cultural characteristics, and 

 one on morphology. Buchanan makes two divisions of the same group by morphology, 

 with a second division by physiological needs and further subdivisions on different 

 bases for different groups. Castellani and Chalmers divide their family of Bacillaceae 



