THE GENERAL CONDITIONS OF EXISTENCE AND DISTRI- 

 BUTION OF MARINE ORGANISMS. 1 



By Dr. John Murray, 



of Edinburgh. 



Since the great geographical discoveries at the end of the fifteenth 

 and the beginning of the sixteenth centuries which are associated with 

 the names of Columbus, Da Gama, and Magellan, there have been no 

 additions to the knowledge of the surface of our planet that can in any 

 way compare with those which have resulted from the exploration of the 

 great ocean basins during the past quarter of a century. The French, 

 the Germans, the Americans, the English, the Norwegians, the Italians, 

 the Swedes, the Austrians — indeed, nearly all civilized nations — have 

 taken part in these explorations, and the result has been a vast accu- 

 mulation of new observations and new facts. 



Whenever science is enriched by a large number of new observations 

 in new regions a change almost invariably follows in our theoretical 

 conceptions. Indeed no complete theory of the earth was possible so 

 long as we were ignorant of the three-fourths of the earth's surface 

 covered by the waters of the ocean. We are very far from having any- 

 thing like a complete knowledge of the physical and biological condi- 

 tions of the ocean, but we know very much more than we did thirty 

 years ago, and it is to some of these additions to our knowledge of the 

 ocean that I propose to direct your attention to-day, especially those 

 having a more or less direct bearing on biology. 



The observations themselves are good for all time. The deductions I 

 may draw from them may be erroneous and evanescent, still it may be 

 interesting to you to catch some glimpse of how one who has spent 

 over twenty years in the study of oceanic phenomena has been cutting 

 paths through the almost impenetrable forest of observations that has 

 grown up in recent years. 



Although we have still no accurate knowledge of the depth over 

 large areas of the ocean, yet deep-sea soundings have in recent years 

 become so numerous that it is probable the contour lines laid down on 

 the most recent maps will not be greatly altered, so far as their general 



1 From Societe" Ne"erlandaise tie Zoologie. Conipte-Kendu ties Seances du Troisieme 

 Congres International de Zoologie. Leyde. 16-21 Septembre, 1895. Leyde: E. J. 

 Brill. 1896. pp. 99-111. 



397 



