189 1.] Marine Organisms. 75 



WEEKLY EVENING MEETING, 



Friday, February 28, 1896. 



Edward Frankland, Esq. D.C.L. LL.D. F.E.S. Yice-President, 



in the Chair. 



John Mdrray, Esq. LL.D. Ph.D. D.Sc. F.R.S. 



Marine Organisms and the Conditions of their Environment. 



Thk ocean may be divided into two great biological regions, viz. the 

 siiperj&cial region, including the waters between the surface and a 

 depth of about 100 fathoms, and the deep-sea region extending from 

 the 100 fathoms line down to the greatest depths. The superficial 

 region may be subdivided into two proviuces, viz. the shallow-water or 

 neritic province around the land masses where the depth is less than 

 100 fathoms, and the pelagic province, embracing the superficial 

 waters of the ocean basins outside the 100 fathoms line ; these two 

 provinces contrast sharply as regards physical conditions, which are 

 of great variety in the neritic province, and very uniform over wide 

 areas in the pelagic province. 



Temperature is a more important factor in determining the 

 distribution of marine organisms, mostly cold-blooded, than in the 

 case of terrestrial species, mostly warm-blooded and air-breathing 

 animals, the distribution of which depends rather upon topographical 

 features than upon climatic conditions. 



A map was exhibited showing the range of temperature in 

 the surface waters of the ocean all over the world, and indicated 

 northern and a southern circunipolar areas with a low temperature 

 and small range (under 10° F.), and an almost circumtropical area 

 with a similar small range but high temperature ; in temperate 

 regions the range is greater, the areas of greatest range (over 40° 

 F.) being found off the eastern coasts of North America and of Asia 

 and south of the Cape, due to the mixture of currents from different 

 sources, which sometimes causes the destruction of enormous numbers 

 of marine invertebrates and fishes. 



The pelagic tropical waters of the ocean teem with various forms 

 of life, of which probably 70 to 80 per cent, function as plants, 

 converting, under the influence of sunlight, the inorganic constituents 

 of sea- water into organic compounds, thus forming the original source 

 of food of marine animals both at the surface and at the bottom of 

 the sea. 



The number of species living in the pelagic waters of the tropics 



