406 PROF. EMRENBERG 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 widely extended layers, containing fossil plants and 
fishes. A single druggist’s shop in Berlin consumes yearly more than 
20 ewt.: the consumption therefore of infusoria as tripoli and for 
casting-moulds in Berlin and the environs may be perhaps estimated at 
50 to 60 ewt. 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 
may be compared with the polygastric bladders of the infusoria, and others 
with the crowned ovary. 5. The infusoria are propagated, besides the highly 
probable ege-formation, not by buds as in plants, but also distinctly by separa- 
tion, a method of propagation which is wanting in all decided plant-formations, 
but which is observed in many decided animals. 6. Some forms, whose motion 
is very slow, or which attach themselves like oysters, afford no reason why they 
are therefore to be considered as plants. Compare the Report of the Academy 
of Berlin, 1836, p. 34. 
