

PRESIDENT'S ADDRESS. Ixiii. 



In all the deeper zones the number of genera is very large relatively 

 to the number of species. Thus the 153 undoubtedly sea-bottom- 

 living species taken in the zone deeper than 2,500 fathoms belong 

 to 119 genera, whereas in the zone between 100 and 500 fathoms 

 there are 1,887 species to only 771 genera, and in the still shallower 

 from to 100 fathoms there are 4,248 species and only 1,438 zone 

 genera. Many of the deep-sea animals, especially those found in 

 very deep water far from land, show archaic characters and 

 represent ancient groups, but those which flourished in very remote 

 geological periods are not represented at the present day. The 

 ocean had a much higher temperature than at present. Life was 

 either absent, or represented by bacteria and other low forms, as is 

 the case in the Black Sea, where there is an insufficient supply of 

 oxygen to support a deep-sea fauna. It is interesting to compare 

 the very slight development of shell and carbonate-of-lime structures 

 in the cold waters of the polar-seas with the massive coral-reefs of 

 Palaeozoic and even later geological times, when the temperature of 

 the sea must have been 65 or 70 degrees Fahrenheit at the Poles. 

 The carbonate of ammonia secreted by marine animals, decomposing 

 the sulphate of lime in sea water, produces insoluble carbonate of 

 lime for shell making, precipitation taking place very slowly in 

 water of low temperature, but very rapidly in water of high 

 temperature. The Arctic Sea abounded with corals in the 

 Carboniferous age, and it was not until Mesozoic times that a 

 differentiation into zones of climate commenced and a cooling at 

 the poles, where the temperature did not admit of coral reefs in the 

 polar area. Temperature is a more important factor in determining 

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

 the case of terrestrial species, which are mostly warm-blooded and 

 air-breathing animals, their distribution depending rather upon 

 topographical features than upon climatic conditions. The Arctic 

 and Antarctic fauna and flora resemble each other. Of these there 

 are a large number of identical and closely-allied species, though 

 quite unknown in the intervening tropical zone. The great 

 majority of the deep-sea species live by eating the surface layers of 



