He again asserts that these deposits could not be the result of any sudden catastrophe, because of the necessarily long sojourn of the sea to account for the extensive beds of fossil shells, the remains of "infinitely multiplied generations of shelled animals which have lived in this place, and have there successively deposited their débris." He therefore supposes that these remains, "continually heaped up, have formed these shell banks, become fossilized after the lapse of considerable time, and in which it is often possible to distinguish different beds." He then continues his line of anti-catastrophic reasoning, and we must remember that in his time facts in biology and geology were feebly grasped, and scientific reasoning or induction was in its infancy. "I would again inquire how, in the supposition of a universal catastrophe, there could have been preserved an infinity of delicate shells which the least shock would break, but of which we now find a great number uninjured among other fossils. How also could it happen that bivalve shells, with which calcareous rocks and even those changed into a silicious condition are interlarded, should be all still provided with their two valves, as I have stated, if the animals of these shells had not lived in these places? "There is no doubt but that the remains of so many molluscs, that so many shells deposited and consequently changed into fossils, and most of which were totally destroyed before their substance became silicified, furnished a great part of the calcareous matter which we observe on the surface and in the upper beds of the earth. "Nevertheless there is in the sea, for the formation of calcareous matter, a cause which is greater than shelled molluscs, which is consequently still more powerful, and to which must be referred ninety-nine hundredths, and indeed more, of the calcareous matter occurring in nature. This cause, so important to consider, is the existence of _coralligenous polyps_, which we might therefore call _testaceous polyps_, because, like the testaceous molluscs, these polyps have the faculty of forming, by a transudation or a continual secretion of their bodies, the stony and calcareous polypidom on which they live. "In truth these polyps are animals so small that a single one only forms a minute quantity of calcareous matter. But in this case what nature does not obtain in any volume or in quantity from any one individual, she simply receives by the number of animals in question, through the enormous multiplicity of these animals, and their astonishing fecundity--namely, by the wonderful faculty they have of promptly regenerating, of multiplying in a short time their generations successively, and rapidly accumulating; finally, by the total amount of reunion of the products of these numerous little animals.