Notwithstanding the numerous and fruitful researches which have been recently made into the life-history of
Bacteria,
our knowledge of the common and interesting curved and spiral forms—
the Vibrio
and
Spirillum
of Ehrenberg—has made little or no advance since his time, neither embryonic nor reproductive forms having ever been observed; while even the zooglœa phase, so characteristic of
Bacterium
and
Bacillus,
has only once been mentioned, and then in a different form. A fresh-water aquarium, which has been stagnating since last summer in the Physiological Laboratory of University College, contained in winter vast numbers of ordinary motile
Spirillum.
On recently re-examining the water, one zooglœa film after another having in the meantime formed on the surface, thickened, broken, and sunk, we found that these motile forms had almost disappeared, while the films consisted almost entirely of resting
Spirillum
in a gelatinous-looking matrix, similar to that of
Bacterium
and
Bacillus
. Among these were two or three apparently distinct kinds of filaments, some resting and colourless, others motile, and filled with highly refracting bright yellowish-brown spheres. Such a field is represented in fig. 1.
The ecology and life history of the common frog (Rana temporaria temporaria).
