406 PROF. EHRENBERG ON FOSSIL INFUSORIA. 



ordinary red heat, which has evaporated all organic (particularly ve- 

 getable) carbon,; for the animals then lived, as at the present day, on 

 plants : at a later period the soluble earths may have become separated, 

 while the silex has better resisted all action. Werner, indeed, was of 

 opinion that subterranean fire had formed the Polirschiefer, an opinion 

 which has much in its favour. 



There is a certain remarkable preponderance in quantity of individual 

 species in most of the fossil infusoria whose localities have been men- 

 tioned. Thus the Kieselguhr from Franzensbad consists almost entirely 

 of Navicula viridis ; the mass from the Isle of France of Bacillaria 

 vulgaris ; that of San Fiore of Synedra capitata ; and that of Bilin is so 

 entirely formed of Gaillonella distans that the other species of animal- 

 cules are only scattered through it. 



Finally, the proportion of these animals merits a passing attention. 

 The millions of the tribe of infusoria have often been mentioned, and 

 spoken of almost without consideration of their number, perhaps be- 

 cause little belief is entertained of their corporeality. They have often 

 been regarded as drops of oil and appearances of various kinds ; but since 

 the Polirschiefer of Bilin must be acknowledged to consist almost en- 

 tirely of an aggregation of infusoria in layers, without any connecting 

 medium, these infusoria begin to acquire a greater importance, not 

 only for science, but for mankind at large. The Kieselguhrs occur, 

 it is said, only in nests about the size of a fist or a head, and probably 

 may be of comparatively recent origin. With the Polirschiefer it is dif- 

 ferent; this forms A^idely extended layers, containing fossil plants and 

 fishes. A single druggist's shop in Berlin consumes yearly more than 

 20 CArt. : the consumption therefore of infusoria as tripoli and for 

 casting-moulds in Berlin and the environs may be perhaps estimated at 

 50 to 60 cwt. yearly, and thence we may in some measure infer the sale 

 in Bilin. I hope to receive in a short time more extensive details on this 

 subject : it is sufficient at present to say, that the infusoria supply all the 

 requisite demands for purposes of practical utility. Passing over the 

 share they have in the Raseneisen, the soldier cleans his arms with tri- 

 poli ; the worker in metal, the locksmith and the engraver polish with 



may be directly recognised in many forms. 3. By a close examination all the 

 apertures may be seen, which may be considered as apertures of nutrition, of 

 generation, and of motion. 4. Internal organs may be distinguished, which 

 niaj- be compared with the polygastric bladders of the infusoria, and others 

 with the crowned ovary. 5. The infusoria are propagated, besides the highly 

 probable egg-formation, not by buds as in plants, but also distinctlj' by separa- 

 tion, a method of propagation which is wanting in all decided plant-formations, 

 but which is obser cd in many decided animals. 6. Some forms, whose motion 

 is very slow, or which attach themselves like oysters, afford no reason why they 

 arc therefore to be considered as plants. Compare the Report of the Academy 

 of Berlin, 1836, p. 34. 



