Page:Popular Science Monthly Volume 15.djvu/789

Rh this view has lately been substantiated by the deep-sea investigations of English naturalists. Wyville Thomson says: "There can be no doubt whatever that we have forming at the bottom of the present ocean a vast sheet of rock which very closely resembles chalk; and there can be as little doubt that the old chalk, the Cretaceous formation, which in some parts of England has been subjected to enormous denudation, and which is overlaid by the beds of the Tertiary series, was produced in the same manner and under closely similar circumstances"; and he also thinks it is "probable that in the deeper parts of the Atlantic a deposit, differing possibly from time to time in composition, but always of the same general character, might have been accumulating continuously from the Cretaceous, or even earlier periods, to the present day." What enormous swarms and successive generations of rhizopods have existed, to effect such amazing results! Were all the extinct chalk animals resurrected at once, they would envelop the earth as did the primitive waters before the land was apart from the sea; we should have an ocean of protoplasm filled with their shells. Figuier truly says: "With these microscopic animals Nature has worked wonders in geological times; nor have those wonders ceased in our days."

Their diminutive size, marvelous reproductive capacity, and tenacity of life, together with the readiness with which they adapt themselves to new and various conditions of existence, not only have insured them a wide distribution in space, but also have enabled them to survive the destructive causes which exterminated higher forms through long and successive ages of geological time. Among about one hundred and twenty-five kinds (genera) of shelled, root-footed animals, only about fifteen are not fossil. Of the one hundred and ten species of those with perforated shells now living in the Atlantic chalk-ooze, the number of species common to it and the various geological formations in England is estimated as fifty-three with the crag, twenty-eight with the London clay, nineteen with the chalk, seven with the Rhsetic and Upper Trias, one with the Permian, and one with the Carboniferous. The survival of so many species in the group is a striking testimony against the theory that the species of each geological division of time ended in a totally demolishing and exterminating catastrophe. The links in their chain are small but numerous, continuously uniting the organic life of remote ages with that of to-day.

At present the immense numbers of their shells on some shores is remarkable; indeed, the sands of some localities are largely composed of them. D'Orbigny obtained 3,800,000 porous shells from a single ounce of sand on the shores of the Antilles. According to Soldani, one ounce of sand from Rimini, on the Adriatic, yields 6,000 shells. This scientist described and figured a great number of these in Italy, publishing an elaborate folio work with 228 copperplate illustrations,