The notion that animals can live and flourish in the sea, at the vast
depths from which apparently living _Globigerinoe_; 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 sight appear to be, that the _Globigcrinoe_ 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 _Globigerinoe_, 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 _Diatomaceoe_, 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.
And considering how large a surface these bodies expose in proportion to
their weight, it is probable that they occupy a great length of time in
making their burial journey from the surface of the Atlantic to the
bottom.

But if the _Radiolaria_ and Diatoms are thus rained upon the bottom of
the sea, from the superficial layer of its waters in which they pass
their lives, it is obviously possible that the _Globigerinoe_ may be