CLASSIFICATION OF THE BACTERIA. 91 
g. Beggiatoa, Trev. 
Filaments very slender, surrounded by mucous mat- 
ter, rigid, having oscillatory movements. Protoplasm 
white, enclosing numerous granules, which recent 
observations have demonstrated to be crystalline sul- 
phur (Cramer, Cohn). 
The Beggiatoa are found most abundantly in 
thermal sulphur waters, where they constitute 
floceuli, which have been named Glairine, Bare- 
gine. They often live in water not containing 
free oxygen. 
They play a great réle in the elimination of 
sulphur and the disengagement of sulphuretted 
hydrogen in thermal waters. 
Their principal species are : — 
B. alba, Trev. 
A whitish mucous mass enclosing colorless filaments, 
having a diameter of 8.5 to 4 w. In most thermal and 
stagnant waters. 
B. arachnoidea, Rabh. 
Flocculi very minute, snow white, filaments as long 
as broad,—5.4 to 7 pw. In the thermal waters of 
~ Europe. 
B. nivea, Rabh.; B. leptomitiformis, Trev., nearly related 
species, living in the same conditions. 
Cohn and Warming have also described : — 
B. mirabilis, Cohn, articles scarcely flexible, measuring 20 
to 40 p. 
B. minima, Warming, a very small species, very flexible ; 
length 40 p, thickness 1.8 to 2 p. 
4, SPIROBACTERIA. 
This tribe includes the bacteria with undulating 
filaments, or filaments in spirals, more or less de- 
