CLASSIFICATION OF THE BACTERIA. 87 



related to them, the Leptothrix, Beggiatoa, and 

 'Crenothrix. 



1. Fil. with indistinct articulations : 



Fil. very slender, short .... BACILLUS. 



Fil. very slender, long .... LEPTOTHRIX. 



Fil. thick, broad BEGGIATOA. 



2. Fil. articulated distinctly .... CRENOTHRIX. 



The following account of the bacilli has been 

 prepared by the author of the present volume 

 from the descriptions given by Magnin in the first 

 edition, in connection with those of more recent 

 authors, and from his own observations : 



g. Bacillus, Cohn. 



The bacilli are short rods, which may be joined 

 in leptothrix chains, or may grow into long fila- 

 ments, apparently homogeneous, but in which, 

 by the use of staining reagents, the protoplasm 

 is seen to be divided into cubical or slightly 

 elongated masses. Some species have flagella 

 and are motile at a certain period of their 

 life-history ; others are always motionless. They 

 multiply both by binary division and by the for- 

 mation of highly refractive endogenous spores, 

 which are spherical or oval. 



B. subtilis, Cohn ( Vibrio suUilis, Ehrb. ; Ferment 

 lutyrique, Pasteur). 



This is the common " hay-bacillus," a widely 

 distributed species. The elementary rods are 



