282 DISCOVERY REPORTS 



and reduced to manageable proportions. Ideally, such a classification should result in 

 an accurate reflexion of the space/time distribution of various groups of species in 

 response to environmental changes. In practice, it has been recognized from the first 

 that a degree of arbitrary distinction is unavoidable — the degree to which some im- 

 portant species can adapt themselves to environmental change is so enormously varied. 



r I ■.I.I ,,,■ ,7 . ; 



GO 



ao 



120 



Fig. 2. Division of the Antarctic zone into biogeographical regions and areas. 



