154 M. Daubrée on the Deposition, Composition, and 
with green eggs. The animals cannot come in contact with 
the oxygen of the air in any other way than by means of the 
water which moistens the turf; but we cannot doubt that they 
have the power of multiplying. In the subterraneous Navi- 
culz, spontaneous movements have been at times seen, but 
those movements were much slower than in the Naviculzefound 
near Berlin on the surface of the ground. The greatest num- 
ber of forms in the subterraneous bed are not found either 
near Berlin nor in the Baltic Sea, but in the neighbourhood 
of Plieger, among the strata of fossil infusoria, which alter- 
nate with lignites and beds of free-stone. The slender spines 
so characteristic of marine sponges likewise abound, and-ap- 
pear to indicate that this extraordinary phenomenon is of pela- 
gic origin. In some quarters of Berlin, the solidity of build- 
ings is endangered by this bed of living infusoria. M. Ehren- 
berg presents at the same time an extract from five memoirs, 
a translation of which is to be desired for some of our journals 
of natural history. The observations of this philosopher em- 
brace the most distant countries, Dongola, Nubia, the delta of 
the Nile and its mud, the infusoria of North America (214 
species, of which 94 are living and 120 fossil), Siberia, the 
Malvina and Marianne islands. M. Ehrenberg intends to 
publish, at the close of this year, a great work in folio, similar 
to his magnificent publication on living infusoria, entitled— 
Forms of Life and Primitive Organization in the Solid Part of 
the Crust of the Globe ; with thirty-five plates engraved from 
the author’s drawings.* 
On the Deposition, Composition, and Origin of Masses of 
Tin Ore. By M. Davsrzr, as reported on by the French 
Academy of Sciences. (M. Dufrenoy, Reporter). 
Tue use of metals goes back to the remotest antiquity, and 
there is no country where we do not find numerous traces of 
the working of mines of lead, copper, or iron. It is therefore 
natural to suppose, that if there remained anything to be dis- 
* From Comptes Rendus, No. XVIII., 2d Nov. 1841, p. 897. 
