ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
427 
to be fructose. The bacterium was found to secrete invertase. Though 
the exact nature of the gelatinous matrix was not determined, reasons 
are given for concluding that it is really nothing more than the swollen 
cell- walls or sheaths investing the bacteria. These sheaths are probably 
composed of dextran, and their development appears to be favoured by 
the presence of calcium chloride. 
Thames Bacteria.* — Prof. H. M. Ward devotes a third article to 
bacteria isolated from Thames water. Eighteen forms are described, and 
these, though belonging to the same type, are separated into two groups, 
the Proteus and the yellow Proteus, according as they are pigmented or 
not. 
Some of the biological phenomena described are interesting. Thus in 
form No. 51 plates were found to become rapidly liquefied towards the 
end of the second day. This phenomenon was found to be due to the 
fact that the surface of the plate was covered with a bacterial film, one 
•cell thick, so thin that its existence could only be determined by the 
aid of a lens. This invisible film in fact formed the real margin or 
corona of the colony, and its existence affords sufficient explanation of 
the apparently sudden liquefaction. The arrangement of the bacteria 
in the films much resembles, as depicted in the illustration, finger-print 
impressions. The outgrowth from the margins of the films is described 
as closely resembling pseudopodia of Amoebae. The growth and method 
of formation of the pseudopodia were observed by making an impression 
culture on a cover-glass smeared with gelatin. The gelatin-layer was 
dabbed on one of the creeping-films of a two days’ old culture, then fixed 
in a culture cell, and observed as a hanging drop. 
In the second group, that of the yellow Proteus type, seven types are 
•described. The general features which they possess in common are that 
they form thin cloudy colonies on plates composed of coarse and tine 
radiating and much interlaced filaments. They liquefy gelatin more or 
less rapidly. The individual rodlet varies from 1-2 p, to 4-6 p, in 
length, and from 0*5 p,-0*75 p, in breadth. They are quiescent or only 
slightly motile. With age the cultures become moie or less pronouncedly 
yellow. On agar and potato the yellow colour is also observed, but 
there is no growth above 25°. Milk is acidified but not peptonised. 
Thermal Death-point of Tubercle Bacilli-t — Dr. Th. Smith thus 
summarises his experiments with regard to the thermal death-point of 
tubercle bacilli in heated fluids. Tubercle bacilli, when suspended in 
distilled water, normal salt solution, bouillon, and milk, are destroyed at 
60° C. in 15 to 20 minutes. The larger number are destroyed in 5 to 
10 minutes. When tubercle bacilli are suspended in milk, the pellicle 
which forms during the exposure of the fluid to a temperature of 60° C. 
may contain bacilli after 60 minutes. 
Organism of the Root-tubercles of the Alder. } — According to Herr 
L. Hiltner, the organism of the root-tubercles of Alnus and of the Elseag- 
naceae — the Schinzia Aim of Woronin, Frankia sub tills of Brunchorst — is 
* Ann. of Bot., xiii. (1899) pp. 197-251 (3 pis.). Cf. this Journal, 1897, p. 426. 
t Journ. exper. Med., iv. (1899) pp. 217-33. 
X Forstl. uaturw. Zeitschr., vii. (1898) pp. 415 et sea. See Amer. Nat., xxxiii. 
{1899) p. 450. 
