Ill EXPEDITION OF THE " CHALLENGER " 85 



evidence for and against this conclusion appeared 

 to me to be insufficient to warrant a positive con- 

 clusion one way or the other, and I expressed 

 myself in my report to the Admiralty on Captain 

 Dayman's soundings in the following terms : 



" When we consider the immense area over which this 

 deposit is spread, the depth at which its formation is going on, 

 and its similarity to chalk, and still more to such rocks as the 

 marls of Caltanisetta, the question, whence are all these organ- 

 isms derived ? becomes one of high scientific interest. 



"Three answers have suggested themselves : 



"In accordance with the prevalent view of the limitation of 

 life to comparatively small depths, it is imagined either : 1, that 

 these organisms have drifted into their present position from 

 shallower waters ; or 2, that they habitually live at the surface 

 of the ocean, and only fall down into their present position. 



"1. I conceive that the first supposition is negatived by the 

 extremely marked zoological peculiarity of the deep-sea fauna. 



" Had the Globigerince 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 Fcraminifera. But the fact is that the proportion of 

 other For n mini far a 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 Globi- 

 gerince. Again, the relative proportions of young and fully 

 formed Globigerince 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 Pulycistinece [Radii la- 



