328 



THE GEOLOGIST. 



FOREIGN CORRESPONDENCE. 



Communicated by Count Maeschall. 



From the Proceedings of the Imperial Academy of Sciences, Vienna,, 

 October, 1858. 



1. — Parasitic Algce in Shells. 



Certain channels met with in the shells of several Acephalons and 

 Gasteropod moUusca have generally been considered to be nutritive 

 channels, and to stand in organic connection with the pores of these 

 shells. Professor Wedl after close examination of a number of re- 

 cent and fossil specimens, has proved them to be accidental deteriora- 

 tions of the shells, owing their origin to parasitic algse of most delicate 

 structure. In the recent specimens these channels stand in com- 

 munication with exiguous cavities, including pedunculated cellules, 

 filling up the channels themselves, and emitting a great number of 

 lateral ramifications. The presence of Amylum in the nucleus, and in 

 the cellules connected with it, manifests itself by the vivid brown tints 

 they assume when brought in contact with diluted tincture of Iodine. 

 The algse themselves have of course ceased to exist in fossil speci- 

 mens, but the characters of the channels in them, their irregular 

 distribution, their connection with minute cavities, &c., are such that 

 the identity of origin with those observed in living individuals can 

 hardly be doubted. As far as investigations have hitherto proceeded, 

 it may be inferred that fresh-water shells suffer more from these 

 vegetable parasites than those of marine species. 



2. — Native Platina. 



Prince B. Demidoff" has lately presented to the Imperial Mineralo- 

 gical Museum a pepite of native Platina, weighing 11| lbs., found in 

 his mines of Nishney Tagilsk, together with other large masses of 

 the same metal, of which the most considerable have been very 

 liberally offered by the noble owner to the museums of Berlin and 

 St. Petersburg. The Vienna pepite measures 5 inches in length, 4 

 inches in breadth, and 3 inches in height. Its surface is covered 

 with impressions similar to those on several pepites of native gold, 

 indicating its origin within a fissure, and bearing some analogy (as 

 the late P. Partch had remarked long ago) with the superficial im- 

 pressions peculiar to meteoric iron. The impressions are partly 

 filled with chroinate of iron, which is generally associated with 

 native Platina. 



