APRIL 23, 1914] 
NATURE 
independent. In this they differ from stable 
systems which are isochronous. In the unstable 
systems a change, however small, tends to in- 
crease until a limit is reached at which a break- 
down of some sort occurs. Instances might be 
given in great variety in which instability leads 
to a quasi-periodic motion or arrangement. 
Geysers which boil over. at fairly constant inter- 
Fic. 2.—Aeolian sand-ripples at Southbour e. 
vals, the whistling of the wind (here the period 
is the rate of production of eddies round small 
obstacles), and the ladder-like shavings taken off 
various materials by cutting tools, are all cases 
in point, although drawn from such different 
quarters. 
Notice of many of the matters of which the 
BIG. 
author treats, such as snow mushrooms, and the 
ridges trodden out by cattle, must be omitted 
for want of space, and although it must be said 
that the explanations are not as good as the 
descriptions, the book is to be recommended as 
the most interesting collection of observations 
concerning the whole subject which has yet 
appeared. A. MALLocK. 
NOS 221, VOL: Gail 
From ‘‘ Waves of Sand and Snow.” 
Fic. 2. 
MUTATIONS OF BACTERIA. 
ARIOUS alterations in the morphology and in 
physiological characters of certain bacteria 
have been obtained by many observers. Thus 
Bacillus coli, the plague bacillus, and other organ- 
isms show considerable variation 
the cells 
in the size of 
on different culture media; the Bacillus 
prodigiosus, which forms a brilliant red 
pigment when grown at ordinary tem- 
peratures, completely loses the power 
of pigment production after cultivation 
at blood heat, at which temperature 
(98° F.) it grows as luxuriantly as at 
65° F. Twort and Penfold have “edu- 
cated”’ the typhoid bacillus to ferment 
sugars which ordinarily it does not 
attack, and Revis has obtained marked 
varieties of Bacillus coli, morphological 
and physiological, by prolonged culture 
in various media. Minchin holds that 
if there be no syngamy (sexual repro- 
duction, e.g. conjugation) among bac- 
teria, as seems to be the case, the so- 
called species of bacteria are to be re- 
garded as mere races or strains, capable 
of modification in any direction. 
A marked instance of the artificial 
production of mutations of Bacillus an- 
thracis, a particularly well-defined and 
stable bacterial species (Fig. 1), is de- 
scribed by Mme. Victor Henri (Compt. 
vend. Acad. Sci., vol. clviii., No. 14, 
1914, p. 1032). The method employed 
was to expose an aqueous suspension of sporing 
anthrax in a quartz tube to ultra-violet radiations 
for times varying from one to forty minutes, and 
afterwards subculturing. 
Whereas the majority of the organisms was 
killed by this treatment, the ultra-violet rays being 
markedly bactericidal, a few survived. Of the 
Fic. 3. 
latter, while most presented a normal aspect, a 
few showed characters decidedly different from the 
typical anthrax bacillus. The principal of these 
were (a) coccoid forms (Fig. 2) which remained 
stable during a period of two months; (b) thin 
filamentous forms (Fig. 3), not taking Gram’s 
stain, not liquefying gelatin, nor curdling milk, 
and producing an infection different from anthrax 
