STILL FOUND IN A LIVING STATE. 321 
tion of the atmosphere and waters, in accordance with which 
the organic inhabitants have also been modified, and upon 
which their extinction or their thorough transformation, in such 
manner as we find them successively in the crust of the earth, 
has been dependent. The recent organisms could not have 
lived, such is the belief, under the former relations of the earth ; 
and the earlier beings must have died out or have become essen- 
tially modified in order to continue to exist in the altered ex- 
ternal conditions. But the most remarkable commencement of 
an entirely new period of organic beings was to all appearance 
manifest between the secondary and tertiary formations ; since 
the whole series of the earlier organisms up to the chalk or 
secondary formation still linked into one another, and contained, 
among the more than thousands of their species, not a single 
generally-acknowledged recent species; but beginning with the 
tertiary formation, or the beds immediately above the chalk, the 
species were with few exceptions different and mixed with 
some recent ones, so that these, few and scattered in the lower, 
became constantly more numerous in the upper strata, as if the 
day of the life surrounding us, and of our own existence, had 
only begun its dawn above the chalk formation. 
Such being the present state of the science, it seemed advan- 
tageous to communicate to the Academy various well-ascer- 
tained facts, leading to an opposite conclusion, relative to nu- 
merous still actually living animals of the chalk, the number of 
which I have succeeded in increasing considerably since the 
summer vacation, and which form a further continuation of 
some researches read before the Academy at the commence- 
ment of the year (1839). 
I. First traces of recent Animals of the Chalk. 
An accurate distinction of the fossil and recent minute animal 
forms has been effected only of late; the opinions of earlier 
writers, therefore, possess no scientific value. Nevertheless, an 
opinion has recently been here and there entertained, that some 
species of still existing animals were to be found in the chalk. 
Thus Soyer Willemet thought he had found alive, fixt upon Cor- 
sican marine Algze, the Spirolina cylindracea, Lam, which Alcide 
d@Orbigny in 1826 placed among the Foraminifera, a Polytha- 
lamian form, said to be from the Paris chalk, but which is im- 
bedded there in the sand and calcaire grossier*. In the first 
* Grobkalk; equivalent of the London clay.—Eb. 
