184 THE OCEAN 



the continental conditions being pushed far 

 from land towards the north by the presence 

 of floating ice, probably also by the greater 

 abundance of food falling to the bottom in 

 this region, where pelagic organisms are fre- 

 quently killed in large numbers through the 

 mixing of surface currents from different 

 sources and consequently varying greatly in 

 temperature and salinity ; it may also be to 

 some extent connected with the migration of 

 benthonic animals towards the tropics. 



As illustrating the restricted distribution 

 of deep-water forms, it may be stated that out 

 of the 272 species taken in the eight unusually 

 productive hauls in the Kerguelen region just 

 mentioned, not one species was common to 

 the eight stations nor even to seven of the 

 stations ; one species was taken at six stations, 

 one species at five stations, two species were 

 common to four stations, thirteen to three 

 stations, and forty to two stations. At two 

 neighbouring stations, about 120 miles apart, 

 145 species of metazoa were taken, and only 

 twenty-two species were common to the two 

 stations. 



When trawlings and dredgings on different 

 kinds of deposits are compared, it is seen 

 that there is a relatively greater abundance of 

 both individuals and species on the terrigenous 

 deposits contiguous to continental land than 



