122 CLASSIFICATION OF BACTERIA 



changes in another quarter-century and even in a decade, it is likely that the new in- 

 formation will not be morphological. 



When acknowledged experts disagree widely on so complex a subject, an ordinary 

 bacteriologist like myself must avoid as far as possible technical taxonomies end ex- 

 tensive references to authority, of which there is a sufficiency so arranged that any 

 diligent reader can make his own evaluations. To the general reader the main lack is 

 in summaries of opinions which make it possible to omit the individual technical 

 articles. 



The recent classifications and keys due to the industry of Bergey (1923), Buchan- 

 an (1916-25), and the Committee of the Society of American Bacteriologists (191 7- 

 20) with the critical summaries of taxonomic authority by Buchanan (loc, cU,), En- 

 lows (loc. cit.), and others make the entire history of the development of classification 

 readily available. One should note also that not the least service of such attempts at 

 complete classification of a series of organisms, concerning which the authors them- 

 selves are the first to admit our information deficient, is their courage in presenting 

 their plans and ideas for criticism. Unless broad plans of this sort are accessible, re- 

 vision is impossible, since most of us are more particularly concerned with some re- 

 stricted portion of the whole. It is far easier to criticize than to construct, but only 

 out of a combination of construction and constructive criticism can we hope to reach 

 stability. 



At first the whole affair looks extraordinarily discouraging. Each attempt at im- 

 provement meets with a volley of objections (Hall, 1927), and such attempts as seek 

 to break away from conventions of taxonomy have few adherents. Closer study, how- 

 ever, offers more hope. One finds that there is a great deal of acceptance of main 

 groups, and that most of the trouble comes from disagreement as to the rank of these, 

 and from persons studying a comparatively small group and believing that their ar- 

 rangement is the only proper one. 



To my mind the first essential, as brought forward by many, and ignored by as 

 many more, is that bacteria in comparison with higher plants and with animals are 

 notably unstable, and that such conformity to type as we see in pure cultures of Plym- 

 outh Rock chickens, or white rats, or Lima beans is not to be expected. 



The more we study them, the less stable appear the characters on which we base 

 much of our classification. If zoologists find, as they do, that complex multicellular 

 organisms are altered by environment to a point where, had they not been followed 

 through, they would be thought different genera, and the botanists present similar 

 evidence, how much more may we expect environmental modifications of a temporary 

 or permanent character among bacteria? One must admit, of course, that unicellular 

 organisms which divide by simple fission carry heredity in a manner very different 

 from that of more complex forms, each half being supposedly identical with the other; 

 but recent work in variation and in mutations in single-cell cultures has forced a modi- 

 fication of those ideas. There is no a priori reason why a colony of anthrax might not 

 undergo in nature conditions similar to those by which we modify it artificially. Evi- 

 dence that the citrate-using B. coli preceded or followed the non-citrate-using is not 

 yet conclusive. We are told that the development of terminal flagella on a coccus 

 tends to change it to a rod form, and we find that an organism may be changed from 



