rface 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 _Globigerinae_ may be
similarly derived; and if they were so, it would be much more easy to
understand how they obtain their supply of food than it is at present.
Nevertheless, the positive and negative evidence all points the other
way. The skeletons of the full-grown, deep-sea _Globigerinae_ are so
remarkably solid and heavy in proportion to their surface as to seem
little fitted for floating; and, as a matter of fact, they are not to be
found along with the Diatoms and _Radiolaria_, in the uppermost stratum
of the open ocean.

It has been observed, again, that the abundance of _Globigerinae_, in
proportion to other organisms of like kind, increases with the depth of
the sea; and that deep-water _Globigerinae_ are larger than those which
live in shallower parts of the sea; and such facts negative the
supposition that these organisms have been swept by currents from the
shallows into the deeps of the Atlantic.

It therefore seems to be hardly doubtful that these wonderful creatures
live and die at the depths in which they are found.[30]

However, the important points for us are, that the living _Globigerinae_
are exclusively marine animals, the skeletons of which abound at the
bottom of deep seas; and that there is not a shadow of reason for
believing that the habits of the _Globigerinae_ of the chalk differed
from those of the existing species. But if this be true, there is no
escaping the conclusion that the chalk itself is the dried mud of an
ancient deep sea.

In working over the soundings collected by Captain Dayman, I was
surprised to find that many of what I have called the "granules" of that
mud, were not, as one might have been tempted to think at first, the
mere powder and waste of _Globigerinae_, but that they had a definite
form and size, I termed these bodies "_coccoliths_," and doubted their
organic nature. Dr. Wallich verified my observation, and added the
interesting discovery that, not unfrequently, bodies similar to these
"coccoliths" were aggregated together into spheroids, which he termed
"_coccospheres_." So far as we knew, these bodies, the nature of which
is extremely puzzling and problematical, were peculiar to the Atlantic
soundings.

But, a few years ago, Mr. Sorby