far. And it seems difficult to imagine why, had the deposit been
accumulated in this way, _Coscinodisci_ should so almost entirely
represent the _Diatomaceoe_.

"2. The second hypothesis is far more feasible, and is strongly supported
by the fact that many _Polycistineoe [Radiolaria]_ and _Coscinodisci_ are
well known to live at the surface of the ocean. Mr. Macdonald, Assistant-
Surgeon of H.M.S. _Herald_, now in the South-Western Pacific, has lately
sent home some very valuable observations on living forms of this kind,
met with in the stomachs of oceanic mollusks, and therefore certainly
inhabitants of the superficial layer of the ocean. But it is a singular
circumstance that only one of the forms figured by Mr. Macdonald is at
all like a _Globigerina_, and there are some peculiarities about even
this which make me greatly doubt its affinity with that genus. The form,
indeed, is not unlike that of a _Globigerina_, but it is provided with
long radiating processes, of which I have never seen any trace in
_Globigerina_. Did they exist, they might explain what otherwise is a
great objection to this view, viz., how is it conceivable that the heavy
_Globigerina_ should maintain itself at the surface of the water?

"If the organic bodies in the deep-sea soundings have neither been
drifted, nor have fallen from above, there remains but one alternative--
they must have lived and died where they are.

"Important objections, however, at once suggest themselves to this view.
How can animal life be conceived to exist under such conditions of light,
temperature, pressure, and aeration as must obtain at these vast depths?

"To this one can only reply that we know for a certainty that even very
highly-organized animals do continue to live at a depth of 300 and 400