68 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the sensitive film. The action appears to be exerted by liquefying as 
well as by non-liquefying bacteria. Luminous bacteria, e.g. Photobac- 
terium phosphor escens, exert a more powerful action on the photographic 
plate than the non-luminous, and this action is moreover not percep- 
tibly diminished by the interposition of a glass plate. 
Some Thames Bacteria.* — Prof. H. M. Ward describes four bacteria 
which were isolated from Thames water. 
(1) A short colourless bacterium, forming stearine-like colonies, and 
belonging to the type of Bacterium Urese (Jaksch). It is not uncom- 
mon in the Thames. Morphologically it is a coccus about 1 p in 
diameter, non-motile, occurring singly, in pairs, in rows of four, or in 
heaps, and formed by the breaking up of rodlets 2 x 1 ft. On plates at 
12°-15° C., the colonies are white, irregularly circular, radiately striated, 
with indented edges. The gelatin is not liquefied, and after some days 
the centre of the colonies becomes yellowish. On agar the growth is a 
dull waxy white ; the colonies sometimes coalesce to form a film having 
the appearance of a polygonal turbot-scale-like mosaic. On potato the 
growth, at 22°, is yellowish while, dry, waxy. On all the solid substrata 
the colonies are stearine-like. In liquid media a white deposit is formed. 
The organism is easily stained, but not by Gram’s method. It is not 
pathogenic to guinea-pigs. 
(2) A colourless capsuled coccus or bacterium. This organism, when 
examined from plates, is an oval non-motile rodlet, over 1 p long and 
from 0*75-1 ft broad. It is invested by a tough dense zoogloea or 
capsule, which occurs round groups of dividing rodlets as well as round 
individual cocci or rods. The organism was cultivated in the ordinary 
media, and grew well on most. Gelatin was liquefied. The growth, at 
first white, became yellowish in time, especially on potato and agar. 
Beef-broth cultures were pathogenic to guinea-pigs. Observations made 
on hanging drops showed that at temperatures from 23*5°-25° active 
swarming took place. 
(3) A rose-pink Micrococcus. This organism, which occurs as spheri- 
cal cocci, varying in diameter from 0*5-1 *5 ft, is of the type M. carneus 
(Zimm.). This organism is interesting partly on account of the produc- 
tion of red pigment, but also from exhibiting two growth-forms. For 
this Micrococcus forms evident Sarcina- like groups when young and 
growing slowly ; while later, and when development is rapid, the group- 
ing is botryoidal and Staphylococcus- like. The organism was cultivated 
on all the usual media, but only agar, potato, and gelatin gave satisfactory 
results. The gelatin was slowly liquefied. 
(4) A pseudo-bacillus. This occurs as irregular and often curved 
rods 4 X 1 ft, motionless, often with spore-like bodies in them, and 
breaking up into cocci. The cocci are found only in old gelatin cultures. 
No true endogenous spores were observed. The growth is white or 
yellowish-white or flesh-coloured. In broth the motionless rods measure 
2-3 X 1-1*2 ft, and may grow out to segmented filaments 10-12 p long. 
On plates at 12°-15° C. the colonies are yellowish-wliite. Micro-cultures 
in hanging drops of gelatin and of broth showed that the organism was 
not a true Schizomycete, but an oidium stage of an extremely minute fun- 
* Ann. of Bob, xii. (1898) pp. 287-322 (4 pis.). 
