ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 600 
in the slime in the vegetative and spore conditions. Both the water 
and slime species are few in number. Nearly all these bacteria liquefy 
gelatin, are killed by the action of direct sunlight, and none are patho- 
genic. All are aerobic and possess well-marked reducing properties, 
changing nitrates into nitrites. Two species of bacteria were found in 
the mud at a depth of 450 feet and 100 miles from land, and these 
were very frequent close in shore. Hence the forms found in bottom 
mud would seem to have a wide distribution. Bacillus limosus , an 
organism found by the author in the Bay of Naples at a depth of 
3500 feet, is a common inhabitant of the mud of this part of the Atlantic. 
The author describes in detail four forms which are the commonest 
among the few species of the flora found by him : — B. limicola sp. n., 
B. pelagicus sp. n., B. litorosus sp. n., B. maritimus sp. n. 
Filaments of Tubercles of Papilionaceae.* — M. M. W. Beyerinck 
finds, from experiments made with Vicia lathyroides, that the filaments 
of the Papilionaceae tubercles consist of bacterial mucus, and that this 
mucus, which represents the cell- wall of the bacterium, has, in the course 
of the filament formation, either completely excluded the bacterial bodies 
or still includes some of them. It seems worthy of note that the bacteria 
still lying in the mucus have not the bacteroid form, the mucous invest- 
ment forming an impenetrable covering which protects the bacteria 
from the metamorphosing action of the cell-protoplasm, owing to which 
influence the bacteria are converted into bacteroids. 
Action of Gravity on Bacterium Zopfii.f — The interesting paper 
by Drs. R. Boyce and A. E. Evans on the action of gravity upon Bacte- 
rium Zopfii is preceded by a description of the organism, its morpho- 
logical, biological, and cultural characteristics, and is illustrated by 
some excellent photograms. The most important of their remarks, how- 
ever, refer to the phenomenon of negative geotropism exhibited by 
B. Zopfii. The experiments showed that a pinnate growth occurs when 
the surface of the medium is kept in or near the vertical, or when the 
culture is rapidly rotated in the horizontal. When the gelatin surface is 
horizontal, or slowly rotated in the vertical, the growth is irregular. In 
order to demonstrate the upward growth, the temperature and medium 
must be suitable. The action of gravity was tested by causing inoculated 
test-tubes to revolve slowly upon a clinostat; under these conditions 
the growth was irregular, while centrifugal force, like gravity, induced 
a regular growth. B. Zopfii is therefore negatively geotropic. 
In connection with this communication, M. M. W. Beyerinck J states 
that he has noticed the pinnate growth described by the English observers. 
At first geotropism was suspected, but a careful examination showed that 
the cause was the extreme sensitiveness of this organism to differences 
of temperature. The radiations are so influenced by thermotaxis that 
their direction is always towards the warmest place, and consequently 
their arrangement may be altered at will by suitably disposing the 
source of heat. Hence the penetration of B. Zopfii into an animal 
body is due to thermotaxis. 
Perhaps the most noteworthy fact in regard to the organism is the 
way in which it grows into the gelatin, which is not liquefied. 
* Centralbl. f. Bakteriol. u. Parasitenk., xv. (1894) pp. 728-32. 
t Proc. Roy. Soc., liv. (1894) pp. 300-12 (2 pis.). Cf. this Journal, 1893, p. 774 
X Centralbl. f. Bakteriol. u. Parasitenk., xv. (1894) p. 799 
