1913] Life in the Great Oceans 625 



WEEKLY EVENING MEETING, 



Friday, Eebniary 7, 1913. 



Sir Fuancls Laking, IUrt., G.C.V.O. K.O.B. M.D. LL.I)., 



Vice-President, in the Chair. 



Sir John Murray, K.C.B. LL.D. D.Bc. F.R.S. 

 Life in the Great Oceans. 



Thk term Biosphere is now used by nutnralists to designate tluit 

 mantle of living matter which clothes the globe wherever the atmo- 

 spbere, the hydrosphere, and the lithosphere are in contact. Life 

 does not extend very high above, nor very deep below, the surface of 

 the land, but in the ocean it is quite different. Life is present 

 everywhere throughout the mass of ocean waters, from the equator 

 to the poles and from the surface down to the bottom at a deptb, it 

 may be, of six English miles. The conditions which determine the 

 life-histories and distribution of diiferent marine organisms comprise : 

 temperature, light, currents, salinity, viscosity, depth, pressure, and 

 chemical composition of the water. [The methods of capturing the 

 organisms in different levels of the ocean were then explained.] 



Throughout the photic zone, extending down to nearly 8000 feet 

 (^500 fathoms), vegetable life is present, both attached to the shore 

 in shallow water, and floating in the upper layers of the open ocean 

 in the form of vast meadows of unicellular alga3, the dead remains 

 of which fall through the underlying waters to the bottom of the 

 deepest seas, supplying food for the animals inhabiting the inter- 

 iiuMliate and bottom waters. Considering the vast extent of the 

 ocean waters, it may be said that the total quantity of living matter 

 in the ocean greatly exceeds that covering the land-surfaces of tlie 

 globe. 



The ])road facts of an oceanographical biological survey may be 

 thus summed up : In the photic zone there are (1) a littoral and 

 shallow-water fauna and flora ; (2) a surface oceanic fauna and 

 flora ; (8) a mud-line fauna, in depths just beyond 100 fathoms ; 

 (4) an intermediate, or twilight, fauna in the open ocean. In the 

 region below the photic zone there are (5) an archibenthal fauna of 

 the continental slope down to 1700 fathoms ; (6) a deep-water inter- 

 mediate fauna ; and (7) an abyssal benthonic fauna, beyond 1700 

 fathoms. 



Dealing first with plant-life in the ocean, it may be stated that 



