16 THE BACTERIA. 



(Bacterium, Vibrio, etc.) with the punctiform 

 bacteria (Monas) ; and it is necessary to come 

 to the time of MM. Hallier, Hoffmann, Cohn, and 

 the greater number of recent botanists, in order 

 to see these two forms brought together anew. 

 In fact, Ehrenberg defines his vibrioniens, which 

 he arranges between the volvocineae and the 

 closteria " animals, filiform, distinctly or appar- 

 ently polygastric, no mucous membrane, naked, 

 without external organs, with the body (like mon- 

 ads) uniform and united in chains or filiform se- 

 ries, as a result of incomplete division." He 

 included in this class* all filiform bodies gifted 

 with proper movement and formed of articles, 

 dividing them into four genera : — 



1. Bacterium: filaments linear and inflexible; three 

 species. 



2. Vibrio : filaments linear, snakelike, flexible ; nine 

 species. 



3. Spirillum : filaments spiral, inflexible ; three spe 

 cies. 



4. Spirochete : filaments spiral, flexible; one species. 



A fifth genus, including but one species, the 

 Spirodiscus fulvus, with filaments in a helix, in- 

 flexible, disposed in contiguous layers, has not 

 been seen since Ehrenberg. Let us add that 

 Ehrenberg often attributed to them a complex 

 structure, stomachs more or less numerous, a pro- 

 boscis, cilia serving as organs of locomotion, — 

 all characters that more recent observers have 

 failed to find. Nevertheless, we must make an 



