—_— 
June 9, 1923] 
M4 
NATURE 
787 

ments were mostly written in collaboration with 
J. H. Ferris, and now the eleventh part by these 
two well-known American malacologists has just 
come to hand (Proc. Acad. Nat. Sci. Philad., vol. 
Ixxv.). It is as admirable both in descriptions and 
figures as its predecessors, and deals principally with 
those. members of the Helix family that inhabit 
the desert lands of Arizona. The genus Sonorella 
dwells in colonies in the interstices of the screes and 
tumbled talus of the volcanic rocks forming the 
hills of that arid and sparsely inhabited region, 
seldom coming to the surface save in very wet weather. 
nd is therefore an arduous sone 
only to be undertaken by a properly equi 
. expedition. The prospective erent lies in ae 
_ fact that each group of hills seems to have largely 
_ its own species, or variety of snail, and that when 
_ the whole area has been surveyed important deduc- 
tions as to the physical geography of the past ma‘ 
be built up on the evidence of the distribution, pas 
and present, of these molluscan forms. 
Dorsat Eyres oF THE SEA SLuG.—K. Hirasaka 
(Annot. Zool. Japon. x., Art. 17, Dec. 1922) gives an 
account of the dorsal eyes of the amphibious sea- 
slug Onchidium verruculatum, which occurs abund- 
antly near the Marine Biological Station at Misaki. 
The dorsal surface of the slug bears numerous papillae 
_of varying size, some of which are provided with 
eyes, one to seven in number. In the posterior third 
of the body some of the papill are of large size and 
branched, forming the respiratory ‘‘ gill-trees,’’ 
Semper stated that the eyes decrease in number as 
the slug grows, and he put forward the view that the 
_ eyes were in course of degeneration ; but the present 
author shows that Semper was mistaken in his belief 
that the eyes disappear as growth proceeds. The 
cornea of each eye consists of modified epidermal 
cells, below which is a fibrillar connective tissue 
forming a circular sheet containing in its peripheral 
parts circular and radial muscle fibres. The lens is 
composed of a large distal cell and a small proximal 
group of cells, the former differentiated into a distal, 
spherical, more or less homogeneous body, and a 
basal cup-shaped part containing the nucleus. Early 
in development this cell exhibits a nerve issuing from 
its base, but the nerve becomes atrophied in the fully 
developed eye. The proximal lens cells form a 
group of usually three or four nucleated cells. Lining 
he proximal two-thirds of the pigmented cup which 
envelops the eye is the retina—a single layer of cells 
loosely packed together, and imbedded in connective 
tissue. In the basal part-of each cell is a large lumen 
filled with a coagulable substance, and proximally 
he cell tapers into a nerve fibre which enters one of 
the nerves passing to the pleural ganglia. 































Minera FEeErtTILIsers.—As a result of three 
residence on the island, Launcelot Owen 
art. Journ. Geol. Soc., vol. lxxix. p. I, 1923) 
q ibes the deposits of tricalcium phosphate that are 
exploited in Ocean Isl., a member of the Gilbert 
group. These have originated in guano, which 
‘gathered in the hollows of a “ karrenfeld,”” worn out 
of upraised coral-limestone. The fantastic features 
_ of this old surface of erosion have been well illustrated 
by G. S. Robertson in his work on “ Basic Slags and 
“Rock Phosphates ’’ (1922), where views of the 
similar surface of Nauru Isl. are also given. L. 
Owen states that the loose friable phosphate is in no 
sense alluvial, but results from the aggregation of 
oncretions. The coral-rock, including the pinnacles, 
became dolomitised, and was then permeated by the 
phosphate down to a depth of fully fifty feet. A 
level exists where the percentage of tricalcium 
NO. 2797, VOL. 111] 
phosphate sinks from its normal 88 to 79 per cent., 
and below this no phosphate deposits of any extent 
are found. The author (p. 13) rejects the idea of 
the occurrence of compounds such as dahllite and 
apatite, and is apparently unaware that the rock of 
BR ratcero, once regarded as pure tricalcium phosphate, 
is now proved to consist of dahllite. He notes (p. 6) 
the occurrence of a translucent isotropic and amor- 
ous phosphate, which he regards as colloidal. This 
is possibly the substance for which A. F. Rogers 
revived the name collophane in 1922. As a contribu- 
tion to our knowledge of potassic fertilisers, the 
U.S. Geological Survey (Bull. 727, 1922) has pub- 
lished G. R. Mansfield’s investigation of ‘‘ Potash 
in the Greensands of New Jersey,” with maps showing 
the distribution of the sands and marls. The 
general characters of glauconite as a fertiliser are now 
well known ; its application to the land is beneficial, 
though it may not equal in effect the recently described 
“potash shales’’ of Illinois (Illinois Univ. Agric. 
Station, Bull. 232, 1921.) 
SYNTHETIC Marsie.—The generally accepted 
theory of the igneous formation of marble rests on 
crude experiments made by Hall (1801-3), in which 
chalk was heated in a closed gun-barrel. In the April 
number of the Journal of the Chemical Society Dr. 
M. Copisarow describes some interesting experiments, 
which tend to support an aqueous origin of marble. 
When solid calcium chloride and hydrated sodium 
carbonate, or a paste of precipitated chalk and sodium 
chloride solution were heated in an autoclave at 
300° at a pressure of 24 atmospheres for 8 hours, a 
compact mass of marble, capable of taking a high 
polish, was formed. The salts present facilitated the 
solution of the chalk or other form of calcium car- 
bonate and the high pressure conditioned crystallis- 
ation. When sodium sulphate was used with 
calcium chloride a compact mass of alabaster was 
formed. 
SEA-LEVEL CHANGES IN DENMARK.—An investiga- 
tion of a submerged peat-bog in the harbour of 
Rungsted, Denmark, by Dr. Knud Jessen, of the 
Danish Geological Survey, has revealed considerable 
changes in relative levels of sea and land in the 
neighbourhood of Copenhagen during the late-glacial 
ae (Danmarks geolog. Undersdg. Rek. iv. Bd. 1). 
About 260 metres off the coast, and at a depth beneath 
the surface of the sea of some 20 metres, was found 
a fresh-water clay— Dryas-clay ’’—containing land 
plants, and this was overlaid first by deposits con- 
taining, among other things, bones of a vole and of a 
wild pig; secondly, by peat containing oak, alder, 
hazel, etc.; and, finally, by sea-mud with cockle 
shells and recent sea-sand. The indications seem to 
be that, at the beginning of the late-glacial period, 
the sea was 18 metres higher at Copenhagen than 
now, and that elevation of the land took place later, 
so that at the end of the late-glacial period it stood 
at least 24 metres above its present level relative to 
the sea; this elevation persisted from the younger 
Dryas-period till the Littorina submergence, which 
finally broke the land-connexion between Seeland and 
Scania. 
VERTICAL MOVEMENTS OF THE ATMOSPHERE.— 
Mr. I. I. Kassatkine, in his monograph of the above 
title which has been published in the Bulletin of 
the Imperial Society of Naturalists in Moscow, 
1915, puts forward a theory of rain formation. 
According to this theory, upward currents of air, 
on reaching the cloud level, cause still further 
separation of moisture by raising the clouds. The 
‘drops thereupon coalesce to form larger ones, which 
