488 
of the Asama-yama; those of the second type were 
invariably the result of explosions of the volcano. 
Some of the most interesting of Prof. Omori’s 
results relate to the areas over which the volcanic 
detonations were heard and the ashes deposited. 
The detonations were produced entirely by air-waves, 
and were often heard as far as 180 miles from the 
volcano, although the shaking of the ground was 
insensible in its immediate neighbourhood. As a 
general rule, the sound-area diverged from the 
Asama-yama as apex towards the east or south-east, 
the sound being unheard at a short distance to the 
west of the volcano. In some cases the direction of 
greatest extent of the sound-area did not differ much 
from that of the prevailing surface-winds; in other 
cases it differed widely, or was even contrary. In 
two explosions the sound-area consisted of two de- 
tached portions, one including the Asama-yama, the 
other some fifty or sixty miles farther to the west. 
In one explosion only, the sound-area diverged from 
the vicinity of the mountain towards the north-east. 
But in neither of the last two types is there any 
relation between the distortion of the sound-area and 
the direction of the surface-wind. 
The areas of ash-precipitation are generally 
narrow and triangular, the directions varying, with 
one exception to the west, from east-north-east to 
east-south-east, being usually in the latter direction. 
These areas are roughly symmetrical with respect to 
the sound-areas. The velocities with which the ashes 
were carried varied from thirty-eight to seventy-eight 
miles an hour, these being much greater than the 
velocities of the surface-winds at the time. 
Prof. Omori concludes that the principal direction 
of extension of the sound-area is the same as that of 
the wind prevailing in the upper strata of the air, 
probably at a height of about five or six miles, this 
being the height generally attained by the columns 
of smoke which rose from the volcano. 
C. Davison. 
THE FRESH-WATER FAUNA OF CENTRAL 
EUROPE.} 
pECE ZSCHOKKE’S (1) monograph, which is pro- 
vided with three excellent maps, gives a detailed 
account of the present state of our knowledge of the 
composition, distribution, and biology of the deep- 
water fauna of the lakes of central Europe. For pur- 
poses of description the lakes are divided into sub- 
alpine and high-alpine series. Lake Lucerne is taken 
as a prototype of the former, and an account is given 
of its various basins and their deep-water organisms. 
One hundred and ninety-eight samples of the bottom, 
including some from the maximum depth (214 metres), 
have been taken, and have been examined by various 
workers. The bottom of this lake (and of other sub- 
alpine lakes) is covered with fine mud, in which 
vegetable remains—fibres, leaves, pollen of conifers, 
&c.—are everywhere present, and in some _ places 
abundant. Among this material large numbers of 
Oligochzeta, Nematoda, and insect-larvz thrive. 
The author gives a list of 141 species of deep-water 
animals—Protozoa, Coelentera, Turbellaria, Nematoda, 
Rotifera, Oligochzeta, Hirudinea, Polyzoa, Crustacea, 
Hydracarina, Insecta, and Mollusca—occurring in 
Lake Lucerne, the range of depth and locality of 
each species being indicated. He then proceeds to 
1 (1) “Die Tiefseefauna der Seen Mittelevropas.” Eine geographisch- 
faunistische Studie. By Prof. F. Zschokke. Pp. vi-+246+3 maps. (Leipzig : 
Dr. Werner Klinkhardt, 1911.) 
(2) “Der Grossteich bei Hirschberg in Nordbéhmen.” Naturwissen- 
schaftliche Untersuchungen veranlasst und herausgegeben von der Gesell- 
schaft zur Foérderung deutscher Wissenschaft, Kunst und Literatuc in 
3éhmen. IT. ‘‘ Die Biologie der litoralen Cladoceren.” Untersuchungen 
liber die Fauna des Hirschberger Grossteiches. 1 Teil. Ry Dr. V. H 
Langhans. Pp. viii+1or+62 figs+30 plates. (Leipzig: as above.) 
NO. 2228, vor. 89] 
NATURE 
(Joy 11, tone 
the systematic description of the deep-water fauna of. 
the sub-alpine lakes in general, an account of each 
order or sub-order prefacing the remarks on the 
constituent species. he notes on each species indi- 
cate in which lakes it has been found, the range of 
depth at which it occurs, and there are in many cases 
observations on the biology, or on any special features 
presented by the distribution, including comments on 
the range of the species in other countries. 
There is an interesting discussion on the ‘‘ Kimmer- 
formen’”’ of the deep-water Mollusca, which are dis- 
tinguished from their shore-dwelling relatives by their 
small size, fragile shells, and peculiar form. The 
author points out that, for instance, in the case of 
specimens of Pisidium living in deep water, the still- 
ness of the water makes the secure closing of the 
shell and well-developed hinge-teeth superfluous, the 
poverty of food accounts for the small size and the 
frailty of the shells, the equalisation of the seasons 
and the vanishing of differences of temperature cause 
the annual rings to become indistinct or to vanish 
altogether. He maintains that the deep-water 
Lamellibranchs are the remnants of a glacial fauna, 
which, in its present refuges, has retained the old 
glacial ‘‘Ktimmerform.”” These forms are, therefore, 
not secondary, as they have been regarded, but 
ancestral. 
The deep-water fauna in general, especially the 
Rhizopoda, Turbellaria, Entomostraca, and Hydr- 
acarina, is shown to be a mixture of elements of two 
chief kinds. Some of the organisms represented are 
to be found within wide limits of temperature (eury- 
thermic), and are truly cosmopolitan; others are re- 
stricted to waters of low temperature (stenothermic), 
and are to be regarded as the remains of a glacial 
or post-glacial fauna. The expectation of some earlier 
writers, that the investigation of the deep-water fauna 
would reveal a centre of origin of new species, is not 
realised. 
(2) This memoir forms the second part of the 
account of the natural history of this * Grossteich,” 
a small lake about 3 and 1-6 km. in extreme length 
and width respectively. The obiect of the researches, 
begun in 1899, and carried on since 1908 by the aid 
of a laboratory built near the lake, has been the 
complete investigation of the general biological 
phenomena of a single water-basin; in fact, an in- 
tensive study of these phenomena, in a small, suit- 
able, and easily accessible lake. The investigation 
has been divided into sections, dealing respectively 
with the geological, hydrographical, chemical, 
botanical, and zoological aspects, each in charge of a 
separate worker. 
The present volume contains a record of the 
faunistic and biological observations on the littoral 
Cladocera, prefaced by a description of the lake, of 
the surrounding hilly country, and of the sources of 
water supply. The qualitative and quantitative appa- 
ratus used in collecting the aquatic organisms of the 
lake is described ; this included a “rotator,” practically 
a short half-cylinder, which by a rapid turn can be 
made to take, by a single scoop, a sample of the 
surface water down to a depth of about 50 cm. A 
list of fifty-nine species of littoral Cladocera from this 
lake is given. Doubtless the great variety of the 
shore conditions accounts for the richness of the 
fauna, but the large number of species recorded is 
due to the numerous collections made and to the 
careful studv devoted to them. The author remarks 
that probably a few (about nine) species niay be added 
to his list by subsequent researches, as several well- 
known Cladocera have not yet been taken in the lake, 
e.g. the genus Bythotrephes, and Bosmina longispina 
and its relatives. 
For faunistic purposes the lake is divided into eight 
————— 
