84 Anniversary Meeting. [Nov. 30, 



has been no less fruitful of results than the two preceding ; which is the 

 more satisfactory, as she has lost the services of her indefatigable Com- 

 mander Captain INares, who, as you are aware, has been summoned home 

 to command the Polar Expedition. Interesting discoveries seem literally 

 to have crowded along the course of this vessel, and the scientific store- 

 houses of the deep to have been unlocked at the bidding of Professor 

 Thomson and his busy and able staff. It would be premature to estimate 

 as yet the probable importance to Biology, Greology, and Physical Geo- 

 graphy of the grand but still imperfect generalizations which are being 

 drawn from the facts sent home from the ship as to the nature and dis- 

 tribution of those microscopic forms of pelagic life, the Poraminifera and 

 Eadiolaria ; but there can be no doubt that our knowledge of the formation 

 of Azoic clays and schists, and of the processes of metamorphism at great 

 depths, is being greatly enlarged by the operations of the 'Challenger ' Expedi- 

 tion. Nor are the discoveries in submarine geography of less interest — such 

 as the finding in the Melanesian Pacific areas which, though only partially 

 circumscribed by islands, exhibit biological and hydrographical phenomena 

 differing widely from those of the circumambient ocean. In the depths of 

 the sea, as on the surface of the land, are contiguous areas peopled by very 

 different assemblages of living things. As on the land we ascend to meet 

 a colder temperature, accompanied by forms of life of wider distribution 

 than at lower elevations, so in the seas of warm and temperate regions 

 we descend to meet with analogous conditions. The ocean thus mirrors 

 one of the most striking features of the distribution of terrestrial life, and, 

 mirror-like, it turns the picture upside down. Purthermore, this ana- 

 logy is confined to the warm and temperate zones of the sea : in the cold 

 zones this order of things is reversed ; there, as on land, we descend to 

 warmer temperatures, and the deepest sea is peopled by animals proper 

 to a much lower latitude. The total result is a uniformity in the general 

 distribution of oceanic life that has no parallel on land ; and facts in the 

 migration of marine animals and plants that were formerly accounted for 

 by assuming that they possessed greater powers of withstanding changes 

 of temperature, are now accounted for by conditions more closely resem- 

 bling those that obtain on the land. 



Prom such considerations as these it would follow that pelagic life 

 should be less differentiated than terrestrial; and no doubt it is so; 

 and to a still more considerable degree is lacustrine and fluviatile life less 

 various than pelagic, in respect of plants especially. On the other hand, 

 whereas both the mass and variety of vegetable life is much greater on 

 land, the bulk, but not the variety, of animal life is much greater in the 

 ocean. It is no doubt owing to the infinite variety of food that terrestrial 

 animals have access to, rather than to the diversities of climate, soil, and 

 other conditions, that the land presents so much greater a variety of life 

 than the sea does. It is true that local assemblages of marine plants 

 have their local faunas, as the Sargasso Sea and the vast Macrocystis^ 



