"Had the _Globigerinoe_ been drifted into their present position from shallow water, we should find a very large proportion of the characteristic inhabitants of shallow waters mixed with them, and this would the more certainly be the case, as the large _Globigerinoe_, so abundant in the deep-sea soundings, are, in proportion to their size, more solid and massive than almost any other _Foraminifera_. But the fact is that the proportion of other _Foraminifera_ is exceedingly small, nor have I found as yet, in the deep-sea deposits, any such matters as fragments of molluscous shells, of _Echini_, &c., which abound in shallow waters, and are quite as likely to be drifted as the heavy _Globigerinoe_. Again, the relative proportions of young and fully formed _Globigerinoe_ seem inconsistent with the notion that they have travelled 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 fathoms, inasmuch as they have been dredged up thence; and that the difference in the amount of light and heat at 400 and at 2,000 fathoms is probably, so to speak, very far less than the difference in complexity of organisation between these animals and the humbler _Protozoa_ and _Protophyta_ of the deep-sea soundings.