On the ' Porcupine ^ - Ejq>edttion Madi'cporaria. 295 



associated with them at a depth of 7U5 fathoms, Tliis is a fauna 

 which, if covered up and presented to the paheontologist, would be, 

 and woidd have been for some years past, considered a deep-sea 

 one. 



It is a fauna which indicates the existence of the same processes 

 of nutrition and of destructive assimihition and reproduction which 

 are reco<;nized in association with corresponding forms at less depths 

 and in higher temperatures. 



The great lesson which it reads is, that vital processes can go on 

 in certain animals at prodigious depths, and in much cold, quite as 

 well as in less depths and in considerable heat. It suggests that a 

 great number of the Invertebrata are not much affected by tempera- 

 ture, and that the supply of food is the most important matter in 

 their economy. 



The researches of Hooker, who obtained Polyzoa and Foraminifera 

 in soundings at a depth of nearly 40i • fathoms off the icy barrier of 

 the South Pacific, of WaUich in the Atlantic, and of Alphonse Milne- 

 Edwards in the Mediteri'anean have had much intiucnce upon 

 geological thought in this age, which, so far as geologists arc con- 

 cerned, is remarkably averse to theory. For many years before any 

 very deep soundings had been taken with the view of searching the 

 sea-bottom for life, geologists had more or less definite opinions con- 

 cerning the deposition of organisms in sediments at great depths. 

 Certainly more than thirty years ago dee^vsea deposits were sepa- 

 rated by geologists fi'om those which they considered to have been 

 formed in shallower seas. The finely divided sediment of strata con- 

 taining Chnoids, Brachiopods, Foraminifera, and simple Madrepo- 

 raria was supposed to have been deposited in deeper water than 

 formations containing large pebbles, stones, and the moUusca whose 

 representatives now live in shallows. The relations of such strata 

 to each other during subsidence, the first being found occasionally to 

 overlap the last, proved that there was a deeper sea fauna in the offing 

 of the old shores whicli were tenanted by littoral and shallow-water 

 species. The deposition of strata containing Foraminifera, Madrepora- 

 ria, and Echinodermata, whose limestone is remarkably free from any 

 foreign substances, has been considei'ed to have taken place in very 

 deep water ; this theoiy has been founded upon the observations of 

 the naturahst and mineralogist. Indeed no geologist has hesitated 

 in assigning a great depth to the origin of some deposits in the 

 Laurentian, Siliman, or in any other formation. The " flysch," a 

 a great sediment of the Eocene formation, has been considered to 

 have been formed at a gi-eat depth and under great pressure. Its 

 singularly unfossiliferous character was supposed to be due to the 

 absence of life at the depths of the ocean where the sediment collected. 

 But this was a theory of the early days of geology, when the de- 

 structive infiuence of chemical processes in strata upon the remains 

 of organisms in them was hardly admitted. 



The great value of such researches as those so ably carried out by 

 Thomson, Carpenter, and Jeftreys is the definite knowledge they 

 impart to the geologist, who is theorizing in the right direction, but 



