7i8 



DEPTHS OF THE OCEAN 



run off-shore and on the eastern side run towards the land. 

 The distribution of the Sargasso weed also furnishes evidence, 

 for, wherever found it has actually been derived from the shore, 

 and, as we know, the Sargasso weed covers a vast area of the 

 western part of the Atlantic. Even the Sargasso weed must 

 become detritus. Hensen has shown that the tufts of this weed 

 gradually become overgrown with heavy bryozoa, which causes 

 them to sink, and then they are gradually disintegrated, being 

 transformed into detritus while sinking, and furnishing nourish- 

 ment for the animals in deep water. During the cruise of the 

 " Michael Sars " the deep waters of the western part of the 

 ocean proved to contain a far more abundant animal life than 

 the corresponding depths in the eastern part. We have seen 

 from Chapter IX. that by far the greater number of the 

 Pteropoda collected, about 3500 or 4000 specimens, were 

 taken in the south-western portion of our track, that is in the 

 Sargasso Sea, and the same remark applies to the pelagic 

 fishes, for instance Cy clot hone 7nicrodon. In giving some 

 figures in support of this, I wish to point out that these figures 

 must only be looked upon as relative values, and are therefore 

 only suited for a comparison between different localities. 



I choose for comparison two stations east of the Sargasso 

 Sea, between the Canaries and the Azores (Stations 42 and 49), 

 and two stations in the Sargasso Sea (Stations 62 and 64), and 

 indicate the number of specimens taken at corresponding depths 

 with the same fishing gear : — 



In northern boreal waters, like the Norwegian Sea, the 

 water-layers of the coast banks cover nearly the whole of the 

 deep area ; we know this because many of the animals which 

 are born on the coast banks are found to have drifted out into 

 the waters above the deep area. Are also the detritus and 

 dissolved substances carried so far from the shore ? How far 

 is the abundant life peculiar to boreal waters due to supplies 



