SCIENTIFIC SUMMARY. 
289 
experiment was the coal-mine of Verpilleux, near St. Etienne. This is 327 
metres, or about 408 yards deep. The temperature at the bottom is very 
constant. The method of experimenting consists in introducing a tube con- 
taining pure gas, such as nitrogen, into the large cavity of the apparatus, 
breaking off its point below the surface of the mercury with which the 
cavity is filled, and screwing the vessel down. Steel tubing, in sections of 
2 millim. bore, is then screwed on to any required length, more mercury 
being forced into the reservoir by means of a powerful force-pump, until it 
mounts to the top of the tube. At each increase of compression the height 
of the mercury-column is measured, and the volume of the compressed gas 
is read off by means of a cathetometer. With nitrogen, compressibility 
slowly increases to a maximum at 65 atmospheres, decreasing again slowly 
to a normal figure at 91, then decreasing rapidly until at 430 atmospheres 
the volume is four-fifths of that given by Marriotte’s law. Having obtained 
a nitrogen standard, other gases could be compared more easily with this 
than examined individually. Tables up to 400 atmospheres were obtained 
for air, oxygen, hydrogen, carbonic oxide,, ethylene, and marsh gas. Graphic 
{representations were prepared, the abscissae representing pressures in metres 
of mercury, the ordinates the difference between the products of the 
pressures into the volume and unity, i.e. to the variation from Mariotte’s 
,law. The most conspicuous variations occur in the case of gases near lique- 
faction. Hydrogen is the only gas not exhibiting a minimum of product of 
pressure and volume. It seems probable that other gases, if forced to 
assume a degree of tenuity similar to that of hydrogen by means, for 
instance, of elevated temperature, would yield curves more and more resem- 
bling those which it furnishes. W. H. Stone. 
ZOOLOGY. 
The Systematic position of the Sponges . — Dr. Conrad Keller supports the 
notion originally put forward by Leuckart, and further developed by Hackel, 
that the Sponges are truly Coelenterate animals, and not Protozoa. At the 
meeting of the Swiss Society of Natural Sciences in August last, he stated 
that at Naples, in the spring of 1879, he had the opportunity of closely 
observing the development of a siliceous sponge, which he named Chalinula 
fertilis, that he ascertained the existence in this sponge of separate sexes, 
and that during the period of reproduction the female presents a nuptial 
dress, her colour varying from carmine-red to blue. The ovum undergoes 
complete but irregular segmentation, resulting in the formation of a larva, 
composed at first of two, and afterwards of three lamellae. He traced the 
transformation of this larva into a young sponge, and, according to him, it 
gave origin to a form which, with the exception of the absence of tentacles, 
agreed in all essentials with a young polype. He considered that his observ- 
ations, in illustration of which he exhibited drawings, prove beyond doubt 
that the true position of the Sponges is among the Ccelenterata, of which he 
would make of them a third natural division (Spongozoa). (. Bibl . Univ., 
December 15, 1879.) 
NEW SERIES, VOL. IY. NO. XV. 
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