16 THE BACTERIA. 
(Bacterium, Vibrio, etc.) with the punctiform 
bacteria (Jonas); 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 volvocineze 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 
cles. 
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 
