36 R. E. BUCHANAN 



of such diverse forms has led most recent authors to divide 

 bacteria into well marked groups. It is the opinion of the 

 author that the larger of these groups should be recognized as 

 genera. The term Bacillus should therefore be restricted, and 

 it would seem that it should be defined more nearly in the terms 

 of De Bary, Zopf, Hueppe, etc., who emphasized the importance 

 of spore production as a diagnostic character. 



The objection may be raised, that a definition of Bacillus as 

 a genus made up of endosporous rods would exclude forms which 

 have lost the power of spore formation but are in other respects 

 closely related. It is evidently impracticable to base generic 

 diagnoses upon a single character. Even though an organism 

 be a variant in one or even more characters, the other resem- 

 blances would be sufficient to include the organism in question 

 in the correct genus. Illustrations of this fact may be taken 

 from higher plants. The Lom,bardy poplar is always classified 

 iiithe genus Populus. It never produces fruit, and it persists solely 

 as the result of vegetative reproduction ; yet the genus Popuius 

 is based in part upon certain fruit characters. The other char- 

 acters are so evidently poplar-like, however, that we do not 

 question the correctness of the assignment of this species to 

 the genus Popuius. 



The genus Bacillus is a relatively large one, and shows some 

 degree of differentiation among the species. It may to advan- 

 tage be divided into subgenera. 



The following key differentiates the subgenera on the basis 

 of their most striking characteristics: 



Key to the subgenera of Bacillus 



A. Spore not barrel-shaped in longitudinal section and not star-shaped in cross 



section. 



I. Motile by means of peritrichous flagella.. Subgenus 1. Eu-Bacillus 

 II. Non-motile Subgenus 2. Bacteridium 



B. Spore barrel-shaped in longitudinal section, longitudinal striations evident. 



Subgenus 3. Astasia 



Subgenus 1. Eu-Bacillus 

 Synonyms : 



Urobacillus Miquel, 1879, p. 517 

 Zopfiella Trevisan, 1885, p. 93 



