ROGER G. PERKINS 129 



rarely in confirmation of species which are already shown to be in close relation. As an 

 aid to differentiation, for such groups as the pneumococci, its value is high. 



THE PROBLEM OF A NEW CLASSIFICATION 



With all these difBculties of a classification based on a variable combination of 

 morphology and chemistry, what are the possibilities of a complete revision? I con- 

 fess it seems to me that unless someone is sufificiently omniscient to foresee the new 

 developments, and to select characteristics which will remain stable for the next hun- 

 dred years there is little hope for such a classification. Man is conservative and 

 would demand proofs of omniscience and prophecy which would be hard to offer. The 

 boldest now in view is that of Enderlein (1925), who believes that morphology is ab- 

 solutely the only important criterion, especially in its development. He decries mono- 

 morphism, mutations, and monocytism, and goes into extensive details as to the 

 minute anatomy of the bacterial cell, with nucleus, sexual and asexual division, re- 

 consideration of the spore, etc. The entire vocabulary is different, so that no com- 

 parison can ])e made. 



PRESENT STATUS OF BACTERIAL CLASSIFICATION 



Reviewing the present status of bacterial classification, what hope does it offer 

 for the future? There is practical unanimity in accepting the class Schizomycetes as 

 first brought forward by Naegeli in 1857. Vuillemin gave a good description and 

 Buchanan (1925) modified it somewhat. Vuil'.emin stated: 



They are simple organisms, formed of a single element without septa and unbranched. 

 The element is circumscribed by a rigid vegetable-like membrane, elastic, but not contractile, 

 sometimes also with a capsule. It may undergo plasmolysis or plasmoptysis. The protoplasm 

 is less differentiated than that of most cells; the chromatin particles do not form an individual 

 nucleus of a permanent type. Division is amitotic. Some forms are motile with flagella which 

 traverse the membrane at points characteristic of the species (polar or diffuse). They are 

 not broader than 5 ix when not in bunches or unimpregnated with metal or colloidal coloring 

 material. The resting stage may be either an arthrospore resulting from a simple modifica- 

 tion of the membrane or an endospore. In some cases the spore-bearing element retains its 

 form or is modified passively by the enlargement of the spore, in other cases it is a specialized 

 element for spore production. Only the latter type of sporulation is satisfactory for generic 

 characters. The amitotic division usually occurs by a pinching transversely with rapid sepa- 

 ration of two individuals. These may remain united into families, in chains, la3'ers or packets 

 as determined by the successive planes of deviation. 



He emphasizes that all forms showing contractility should be placed in the protozoa, 

 that the myxobacteria constitute a distinct group, and that forms like the tubercle 

 bacillus which show branching should be placed in the mold group Microsiphones. 



Buchanan used the following characterization: 



Typically unicellular plants, cells usually small and relatively primitive in organization. 

 The cells are of many shapes, spherical, cylindrical, spiral or filamentous; cells often united 

 into groups, families or filaments; occasionally in the latter showing some differentiation 

 among the cells, simulating the organization seen in some of the blue-green, filamentous 

 algae. No sexual reproduction known. Multiplication typically by cell fission. Endospores 

 are formed by some species of the Eubacteriales [see below], gonidia (conidia, arthrospores) 



