Ekrenberg on Infusoria in Igneous Rocks. 401 



part of a grey basaltic lava-stream proceeding from Seelsberg. The 

 author was indebted to M. von Dechen for this information. 



A careful microscopic examination gave the following singular 

 results with regard to this locality : — 



First : — Not only is the stratum of polishing slate entirely made 

 up of the siliceous cases of infusorial animalcules, but the beds 

 associated with it, consisting, as we have seen, of volcanic tuff and 

 pumiceous conglomerate, are composed in great part of the same 

 substance. 



And secondly, the tuff and pumice conglomerate exhibit the infu- 

 sorial cases in a distinctly fused condition, resembling that noticed 

 by the author in some investigations made several years ago on 

 infusorial earth that had been burnt for tiles or porcelain. 



Thirty-eight species of microscopic infusoria were determined by 

 the author from the Hochsimmer beds, and it seemed probable that 

 many more might be added to the list ; of these species, however, 

 only two are new, and of the remaining thirty-six, one has hitherto 

 been known in Europe only as a tertiary fossil, but all the rest are 

 living European species. 



Before extending his investigations further in the determination of 

 additional species from this locality, the author thought it advisable 

 to advance in another direction, and since the very fragments of 

 volcanic rock themselves had exhibited these organic remains, he 

 availed himself of M. Krantz's collection at Berlin, and selected 

 several different kinds of pumice for examination. He thus obtained 

 a number of specimens of volcanic ash or trass from Brohl on the 

 Rhine, and he afterwards also obtained specimens of similar tuff 

 from Civita Yecchia, and from Posilippo near Naples. All these he 

 carefully examined. 



The result was very striking, since the nature of the pumice was 

 apparent everywhere, and exhibited not merely that peculiar cellular 

 structure which reminds the observer of fused specimens of Gaillo- 

 nella, but every minute fragment, even from the very middle of the 

 mass, exhibited more or less distinctly the contained forms, and a 

 number of species was soon added to the list of those contained in 

 pumice. 



