236 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
at tlie ends, till regular three- or four-rayed stars (and later on six- or 
eight-rayed) were produced. There was no tendency to the pear-shaped 
swelling seen in Pasteuria ramosa, and no spores were noticed. 
Emulsion and Sediment Figures produced by Motile Bacteria.* — 
Prof. W. Beijerinek states that motile bacteria, when occurring in 
great numbers in thin layers of a nutrient solution, form, after being 
allowed to rest for a few minutes, characteristic accumulations. These 
accumulations are either columnar in shape and run up and down right 
through the whole thickness of the fluid, or are flat and lie at the bottom 
of the vessel. In either case the groups or accumulations are sharply 
defined, and are separated from one another by fluid poor in bacteria, 
or devoid of them. The columnar groups are called emulsion-, the flat- 
groups sediment-figures. The former most commonly originate in thick 
fluid media, such as liquefied gelatin ; the latter in thin liquid media, 
such as bouillon. In any case the figures are the result of the specific 
properties of the bacteria, though all mobile bacteria are not equally suit- 
able for the production of emulsion-figures. The emulsion-figures are 
probably caused by local currents ; in the interspaces fluid saturated 
with carbonic acid ascends, while within the columns a liquid medium 
saturated with oxygen descends. The author, after describing Bacterium 
termo, proceeds to discuss the changes caused by currents, by dilution, 
and by chemotaxis. In the course of his remarks the author introduces a 
new word, “ tonotaxis,” or sensitiveness to osmotic variations, and con- 
cludes by describing the influence of an oil-drop. 
Kitre-Fungi.| — In their reply to Winogradsky, who asserted that Ihc 
results obtained by Prof. A. Stutzcr and Heir K. Ilartleb were due to 
unskilful manipulation, these writers give a short retrospect of the 
points at issue, and then clearly state their own view, which is to the 
effect that nitrification is a transitory function of a definite organism, 
which under certain conditions can thrive on organic nutrient media. 
The proof of this is promised later. Meanwhile they mention an inter- 
esting observation which tends to support their view. A pure culture 
of the nitrate organism was transferred to nutrient fluid, the source of 
nitrogen being sodium nitrite. Through the vessels a current of air 
was transmitted. For the first flask the air w’as filtered through cotton- 
wool ; for the second it was passed through a thick layer of strong 
caustic soda solution ; so that, in the one flask, carbonic acid was present, 
in the other not. In the latter vessel had been placed a small quantity 
of glycerin. The vessels were kept in the dark at a temperature of 
25°— 30° C., and after a lapse of about 12 days the microbes in the first 
flask had produced nitrate and had undergone no morphological change. 
In the second flask there was no nitrate, the medium was turbid and con- 
tained numerous rodlets and cocci, and also a raycele similar to that 
which had so frequently spoilt the aqueous nutrient media of previous 
experiments. 
Denitrifying Bacteria and the Loss of Nitrogen caused by them.t 
— Herren K. Burri and A. Stutzer isolated from horse-dung two bacteria 
* Centralbl. Bakt. u. Par., 2 te Abt., iii. (1807) pp. 1-6, 40-7 (1 fig. and 1 pi.). 
t Op. cit., ii. (1897) pp. 6-9, 54-7. Cf. this Journal, ante, p. 145. 
X Ann. Agroii., xxii. (1896) pp. 491-4. See Journ. Cliem. Soc., 1897, Abstr., 
p. 114. 
