with so'fne Notices of American DiatomcB. 123 



mals or vegetables. On burning a great number of Fragillaria pecti- 

 nalis, an animal smell was noticed. Such a smell would, however, be a 

 very indefinite character, for various other Algas produce a similar odor 

 on their being burnt to a coal. After the burning of the Fragillaria pec- 

 tinalis, and various other beings of the same kind, Brebisson found sili- 

 ceous envelops surrounding them in a very perfect state, and precisely 

 similar to those exhibited by the fossil DiatomcE, discovered by C. Fis- 

 cher in the peat-bog near Franzensbad, and which led to those beautiful 

 observations that Ehrenberg made known on this subject in the course of 

 last year.* 



" The results of those latter observations belong properly to geognosy ; 

 t)ut we must add this one remark, that under the fossil Infusoria hitherto 

 discovered, only those beings are to be understood, which botanists, as has 

 been previously shown, receive as plants. The occurrence in a fossil 

 slate of these minute microscopical plants, is caused by the hard siliceous 

 envelop, which resists all destroying influences. Kiitzing's discovery, that 

 the envelop of the Bacillarim consists of silica, which was mentioned in 

 our first year's report, has, by this circumstance, been rendered more im- 

 portant. If we observe the same minute plants in the living state, it often 

 happens, that amongst them some dead ones occur, which exhibit that 

 perfectly transparent and colorless siliceous envelop ; it is therefore proved, 

 that a great mass of such siliceous envelops might also be produced by 

 the decomposition of the plants, or in the moist way, and also that the 

 ^ mountain masses, which consist more or less of such siliceous envelops, 

 might not always be regarded as being produced by the action of heat at 

 the bottom of the sea.t Brebisson tries to bring the DiatomcB into two 

 divisions, viz. the proper Diatomce, which exhibit a siliceous envelop, 

 and the DesmidicB, which are without a siliceous coating, and entirely 

 reducible to carbon. In the more perfect plants, the epidermis of which 

 is penetrated by a siliceous envelop, it would at least be improper to 

 make such divisions ; in this case, hovvever, they may be of some use. 



" In a recent memoir, Mohl has again declared himself against the ani- 

 mal nature of the Badllarice. ' I admit,' says he, 'that the doubt which 

 was raised respecting their vegetable nature is not yet removed ; their 

 animal nature, however, has been as little proved, and we find evident 

 transitions from them to vegetables.' " — Lond. and Ed. Phil. Mag., Oct. 

 1837, p. 385—390. 



* Vide on Fossil Infusoria, Wiegmann's Archiv, 1836, p. 333. A translation of 

 Ehrenberg's two papers on this subject is given entire and with engravings in the 

 Scientific Memoirs, Vol. I, p. 400. — W. F. I have not had an opportunity to see 

 either of these worRs. — -J. W. B. 



t Ehrenberg's opinion is, that these masses owe their origin to the action of vol- 

 canic heat on the bottom of the sea. Vide Scientific Memoirs, Vol. I, p. 400. 



