ANIMAL LIFE 173 



radiolaria and members of some of the higher 

 groups, apparently live exclusively in this 

 area, the limits of their bathymetrical distribu- 

 tion have not been ascertained. So far as 

 they have proceeded the investigations seem 

 to show that the organisms inhabiting this 

 intermediate zone of water are not so numerous 

 as those in the layers nearer the surface and 

 nearer the bottom. 



Benthos. — Passing from pelagic to benthonic 

 animals, it seems to be the general rule that 

 the greatest profusion of bottom-living animals 

 is to be found in coastal waters, and that they 

 gradually decrease in abundance on proceeding 

 farther and farther from land into deeper and 

 deeper water, until a minimum (but not a zero) 

 is reached in the red clay areas of the abyssal 

 plain. Distance from a continental shore 

 seems to be as a rule a more important factor 

 in the distribution of the benthonic animals 

 than actual depth, for hauls at similar 

 depths less than 300 miles from land gave 

 more individuals and species than were 

 obtained in hauls beyond 300 miles from land, 

 except perhaps in the great Southern Ocean, 

 where because of icebergs continental condi- 

 tions are pushed far north of the Antarctic 

 continent. 



The greatest variety of animal life is prob- 

 ably to be met with in the shallow waters of 



