194 



ANIMAL LIFE OF THE DEEP SEA BOTTOM 



But in view of our successful trawls in the Kermadec Trench it is 

 difficult to explain why animals like fishes, brittle-stars, sea-pens, and 

 sea-mats, which were caught only at a little beyond 6,000 metres, were 

 absent from the rich hauls of individuals between 7,000 and 8,000 metres, 

 unless we are to regard pressure as a limiting factor which only a minority 

 of the thousands of species of marine animals have succeeded in over- 

 coming. 



The time set aside for biological work in the Kermadec Trench ran 

 out. It had justified our boldest hopes, but perhaps that was the very 

 reason why we felt so tantalized as we steamed north from Auckland 

 towards Samoa, with the fascinating deep beneath us all the way. The 

 worst moment of all was when the curve of our echo-sounder swung 

 down to 9,700 metres; for, with a correction of plus 294, we were thus 

 only 6 metres short of having found the first trench in the southern 

 hemisphere with a depth of 10,000 metres. It was at 31° 53' S., 177° 05' 

 W.; and there was a fine bed for trawling, should anyone wish to try 

 his hand. 



Deepest Occurrence of Some Animal Groups 



The s>'Tnbol < indicates less than 



Sea-anemones Actinaria 



Echiuroid worms Echiuroidea 

 Sea-cucumbers Holothuroidea 



Bivalves Bivalva 



Bristle-worms Polychceta 



Amphipod crustaceans 



Amphipoda 



Isopod crustaceans Isopoda . . . 

 Tanaid crustaceans 



Tanaidacea 



Sipunculoid worms 



Sipunculoidea 



Sea-lilies Crinoidea 



Gastropods Gastropoda 



Polyps Hydrozoa 



Starfishes Aster oidea 



Sea-urchins Echinoidea 



Cumacean crustaceans 



Cumacea <6,ooo 7,130 i Sunda 



