ANIMAL LIFE OF THE DEEP SEA BOTTOM 1 79 



because the ship drifted over the eastern slope and we preferred a rather 

 shorter trawl at the desired greatest depths to the risk of an admixture 

 from other depths, to say nothing of the danger of a torn trawl on the 

 steep valley sides. This trawl produced 12 sea-anemones four sea- 

 cucumbers, and a bristle-worm belonging to the species represented in the 

 first trawl, besides the remains of five greenish little echiuroid worms and 

 some decaying vegetation washed out from the shore. The bottom sub- 

 stance here consisted of a number of rather firm lumps of clay. 



The third trawl appeared to have been successful, but when we came 

 to hauling in we found that the end 600 metres had got itself wrapped 

 round the trawl, which had consequently failed to fish. Nor did the 

 fourth trawl produce any bottom animals, as the trawl did not reach the 

 bed, despite our usual careful calculations according to Dr. Kullenberg's 

 formula. At the fifth attempt some of the wire again got entangled in 

 the trawl, though this time we obtained some sea-anemones, a sea- 

 cucumber, and a bivalve of the species previously caught, as well as four 

 small crustaceans (isopods. Fig. p. 180). We made a sixth and last 

 attempt, but were so troubled by bottom conditions, current, wind, and 

 weather that we dared not send the trawl to the bottom. For 19 hours 

 we struggled in vain to keep a level bottom long enough to have enabled 

 us to fish the approximately five kilometres astern of us. It was a bitter 

 disappointment to leave the Philippine Trench in this way, but such is 

 the fisherman's lot and it could not eclipse our pleasure at the successful 

 hauls. 



We had found a whole little animal community. All the large groups 

 of invertebrates were represented — polyps, worms, echinoderms, molluscs, 

 and crustaceans (Fig. p. 180). The known depth limit of life had been 

 pushed some 2.5 kilometres lower down; and whereas it might have been 

 doubted whether we should find anything in the Philippine Trench, there 

 is now no reasonable ground for supposing that life cannot also penetrate 

 the few hundred metres further down to the new record depth of 10,863 

 metres in the Mariana Trench, provided that there, too, there is sufficient 

 oxygen in the water. Our finds of a great variety of bottom deposits of 

 clay, gravel, and stones in the Philippine Trench may provide a basis from 

 which to explain why the water masses from the down-flowing depth at 

 about 3,500 metres and beyond (see p. 40) can be so uniform and conse- 

 quently so stable as they are. The general rule is that it takes wind or 

 differences of density to create water-interchanging currents, and here 

 there do not seem to be sufficient differences of density in the water 

 masses. 



