BIOCHEMICAL CRITERIA 313 



ultimately fall into line with better studied features of bacterial economy, but 

 until then we have no a priori grounds for evaluating the biological importance 

 in classification of antigenic structure, or, say, the power of producing a character- 

 istic toxin. 



A. Organisms photosynthetic witli the evolution of oxygen and possessing the typical 

 green plant chlorophylls, phycoeyanin and sometimes phycoerythrin, and colourless, 

 non-photosynthetic counterpart, clearly recognizable as such. 



Division I. Myxophyta. 



B. Organisms not so characterized. 



I. Unicellular or mycelial organisms with rigid cell walls. Motility, when present, 

 by means of flageUa. Endospores, cysts, or conidia may be formed. 



Class 1. Eubacterise. 



(a) Organisms photosynthetic, but not producing oxygen. 



Order 1. Rhodobacteriales. 



(b) Non-photosynthetic organisms. 



1. Unicellular. 



Order 2. Eubacteriales. 

 2. Mycehal organisms. 



Order 3. Actinomycetales. 

 II. Unicellular rod-shaped organisms, without rigid cell walls. Always creeping motility. 

 Microcysts and fruiting bodies may be formed. 



Class 2. Myxobacteriae. 

 One order. Myxobacteriales. 



III. Unicellular, spiral organisms without rigid cell walls. Motility by means of an 

 elastic axial filament or modified fibrillar membrane. 



Class 3. Spirochaetae. 

 One order. Spirochsetales. 



IV. Organisms not faUing into the previous classes. 



Fig. 46. 



Our main trouble is that we have no rules, and the few conventions which take 

 their place are honoured as much in the breach as in the observance. It seems 

 quite clear that nothing but some form of international agreement with regard 

 to classification and nomenclature will put an end to the existing state of chaos. 

 Whether it will be possible to adopt, in their entirety, the rules of botanical 

 nomenclature, is a problem which only the futuje can decide. There are obvious 

 advantages in adopting the Linnaean binomial nomenclature, which has served the 

 purposes of zoologists and botanists in general ; but it is doubtful whether the 

 bacteriologist will not be forced to make frequent use of additional terms, desig- 

 nating races, varieties, or types. The frequent use of trinomial or quadrinomial 

 names is, however, a cumbersome procedure ; and it may be found necessary to 

 regularize the use of letters or numbers, which is a current convention in bac- 

 teriological terminology. The Linnaean admonition, " varietates levissimas non 

 curat botanicus," may serve the turn of the systematic botanist, and the bac- 

 teriologist would probably be well advised to bow to it in naming those groups 



