86 EXPEDITION OF THE " CHALLENGER " m 



rid] 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 Globigcrina, 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 Globi'gerina, but it is provided with long radiating 

 processes, of which I have never seen any trace in Globigcrina. 

 Did they exist, they might explain what otherwise is a great 

 objection to this view, viz., how is it conceivable that the heavy 

 Globigcrina 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 ab-ive, 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 organi- 

 sation between these animals and the humbler Protozoa and 

 Protophyta of the deep-sea soundings. 



" I confess, though as yet far from regarding it proved that 

 the Globigcrina live at these depths, the balance of probabilities 

 soems to me to incline in that direction. And there is one 

 circumstance which weighs strongly in my mind. It may be 

 taken as a law that any genus of animals which is found far 

 back in time is capable of living under a great variety of -circum- 

 stances as regards light, temperature, and pressure. Now, tho 



