The notion that animals can live and flourish in the sea, at the vast
depths from which apparently living Globigerinae have been brought
up, does not agree very well with our usual conceptions respecting the
conditions of animal life; and it is not so absolutely impossible as
it might at first appear to be, that the Globigerinae of the Atlantic
sea-bottom do not live and die where they are found.
As I have mentioned, the soundings from the great Atlantic plain are
almost entirely made up of Globigerinae, with the granules which
have been mentioned and some few other calcareous shells; but a small
percentage of the chalky mud--perhaps at most some five per cent of
it--is of a different nature, and consists of shells and skeletons
composed of silex, or pure flint. These silicious bodies belong partly
to the lowly vegetable organisms which are called Diatomaceae, and
partly to the minute, and extremely simple, animals, termed Radiolaria.
It is quite certain that these creatures do not live at the bottom of
the ocean, but at its surface--where they may be obtained in prodigious
numbers by the use of a properly constructed net. Hence it follows that
these silicious organisms, though they are not heavier than the lightest
dust, must have fallen, in some cases, through fifteen thousand feet of
water, before they reached their final resting-place on the ocean floor.
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