THE 
MONTHLY MICROSCOPICAL JOURNAL. 
SEPTEMBEK 1, 1875. 
I.— On the Existence of Flagella in Bacterium iermo. 
By W. H. Dallinger, F.K.M.S., and J. J. Drysdale, 
M.D., F.E.M.S. 
(Taken as read before the Koyal Microscopical Society.) 
Plate CXIII. 
In the huge Bacterium known as Spirillum volutans, Cohn 
discovered, and figured in his * Eesearches on the Bacteria,' * the 
presence of a pair of flagella, one at each end. This bacterium is 
gigantic in proportions in relation to most other varieties, but 
especially so to B. termo. An idea of their relative proportions is 
given in Fig. 1, PI. CXIII., where a represents B. termo and h 
8. volutans. It is a spiral, and moves through the fluid by swift 
revolution upon its axis. 
In the summer of 1872 some very fine specimens of 8. volutans 
came under our notice, and were carefully examined. We were 
enabled fully to confirm Cohn's discovery, and demonstrated re- 
peatedly the presence of a pair of swiftly lashing flagella ; the 
drawing at h, Fig. 1, was made from a specimen magnified 1300 
EXPLANATION OF PLATE CXIII. 
Fig. 1. — a. B, termo magnified with the same power as 6, which is a specimen 
of Spirillum volutans showing flagella at each end. 
Fig. 2. — B. termo as seen with a power of about 600 diams. 
Fig. 3. — The same, as seen with -g^th and second eye-piece (3700 diams.). 
Fig. 4. — B. termo seen with flagellum at one end, the light coming in the 
direction of the arrow. 
X:;; Fig. 5. — The same object when it moved at right angles to its former position, 
the light coming from the same direction, causing the sight of the flagellum to be 
lost. 
Fig. 6 represents one B. termo which was in a still condition, but one flagellum - 
moving. The light came in the direction of the arrow. When the end marked 
2 h was in focus flagellum was seen, but none at the end c. When the end marked 
1 a was focussed carefully, the flagellum at that end was seen, and lost at the 
end d. 
Fig. 7. — The true form of B. termo. 
Fig. 8. — The form as shown by the supplementary stage " illumination 
hefore flagella were found, showing the pointed termination of the body at a, 6. 
* ' Beitr'age zur Biologie der Pflanzen.' Zweites Heft, p. 127. Breslau. 
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