EVOLUTION AND CLASSIFICATION OF BACTERIA 453 



shown to have peritrichous flagella, the family is probably de- 

 rived from the peritrichic stem, and does not belong near the 

 Nitrobacteriaceae, where it has been placed by the committee. 

 Buchanan, as previously mentioned, has wisely suggested the 

 recognition of a separate order, calling it Actinomycetales. 

 Perhaps the order might be subdivided into two families : Myco- 

 bacteriaceae for forms like the tubercle organism, Actinomy- 

 cetaceae for the forms with true branched filaments. 



All the genera in this group recognized by the committee prob- 

 ably have good standing, with the possible exception of Nocardia 

 which as defined has no suitable type species. 



Family 3. Pseudomonadaceae. This family has good stand- 

 ing, as does the genus Pseudomonas, also; but as already men- 

 tioned, the family might include the autotrophic as well as the 

 heterotrophic forms. The definition of the family should be so 

 worded as not to exclude all spherical or immotile forms that 

 seem to be closely related to typical species. The committee has 

 evidently made a mistake in saying "Flagella single, polar," 

 thus leaving no place for the lophotrichic rods. Many of the 

 fluorescent water bacteria which the committee plainly intends 

 to put in this family have a tuft of four or more polar flagella. 



Family I^. Spirillaceae. The arrangement of this family in 

 two genera, as recognized by the committee, is apparently as 

 satisfactory as any which can be suggested. 



■Family 5. Coccaceae. This family has been studied so thor- 

 roughly by Winslow and Winslow (1908) and its nomenclature 

 given such careful scrutiny by Buchanan (1915) that there are 

 no good reasons for criticising its genera as recognized by the 

 committee. 



The question arises whether this family is primitive or highly 

 specialized. On the one hand the spherical form suggests prim- 

 itiveness, while on the other the large number of animal para- 

 sites it contains plainly indicates recent development. As a 

 matter of fact, the group seems to contain all gradations from 

 soil and water forms that live on material of fairly simple com- 

 position up to parasites that are adapted to growth in living 

 animals. Perhaps eventually we will have to accept Jensen's 



