The ooze in the bed of the Atlantic ocean, as well as of the Mediterranean and Adriatic contains fifty per cent. of Globigerinæ; they exist in the Red Sea, in the vicinity of the West Indian Islands, on both sides of South America and near the Isle of France, but not in the Coral Sea which is occupied by different genera. Though in utter darkness, at the bottom of a deep ocean, these little creatures can procure food by means of their pseudopodia, whose extreme sensibility makes up for the want of sight; and the very excess of pressure under which they live insures them a supply of oxygen at depths to which free air cannot penetrate, for it is believed that the quantity of dissolved air that water contains is in proportion to the pressure. Fossil Foraminifera enter so abundantly into the sedimentary strata, that Buffon declared ‘the very dust had been alive.’ 58,000 of these fossil shells have been computed in a cubic inch of the stone of which Paris and Lyons are built. The remains of these Rhizopods are for the most part microscopic. M. D’Orbigny estimated that an ounce of sand from the Antilles contained 1,800,000 shells of Foraminifera. A handful of sand anywhere, dry sea-weeds, the dust shaken from a dry sponge, are full of them. When the finer portions of chalk amounting to one half or less are washed away, the remaining sediment consists almost entirely of the shells of Foraminifera, some perfect, others in various stages of disintegration. In some of the hard limestones and marbles, the relics of Foraminifera can be detected in polished sections and in thin slices laid on glass. It is now universally admitted that some crystallized limestones which are destitute of fossil remains, had been originally formed by the agency of animal life, and subsequently altered by metamorphic action; the opinion is gradually gaining ground among geologists that such is the history of the oldest limestones.