MIGRATIONS AND DISTRIBUTION 259 



years some Blue and Fin whales had crossed from area III to area IV, and two Fin 

 whales had crossed from the Bellingshausen Sea (area I) into area II. Although the 

 scarcity of whales at the boundary between areas III and IV would suggest a sharper 

 distinction between these two areas than between areas II and III, the recoveries of 

 marks, so far as they go, suggest a more distinct separation of areas II and III, for very 

 few marked whales crossed the Greenwich meridian. One Fin whale marked in area III 

 was captured three years later in area II, and a Blue and a Fin made the same crossing 

 after four years. 



It may be concluded that, just as Blue and Fin whales are less definitely segregated in 

 the different areas than Humpbacks, so they cross more readily from one area to another. 

 Rayner, however, shows that the majority return to the same area after their northward 

 migration. Since out of a considerable number of marks recovered there were no in- 

 stances of a whale crossing from one area to another during the same season it seems 

 likely that the cross over takes place either in temperate regions or in the course of the 

 migration ; but the two Fin whales which moved from the Bellingshausen Sea through 

 the Drake Strait into area II may have done so in a high latitude in summer. 



This segregation of the stocks of whales in the Antarctic has been considered here at 

 some length because it is a matter of primary importance in the problem of the distribu- 

 tion of whales and the effect of whaling on the stock, and it is evident that such subjects 

 as the relative numbers of each species, the age composition of the stock, the effect of 

 whaling, etc., can with advantage be investigated separately for the separate areas, pro- 

 vided that sufficient data are available. There is no doubt that the major communities 

 of whales can be subdivided into smaller groups some of which have been recognized by 

 Hjort, Bergersen, Lie and Ruud, and by Rayner, as certain minor concentrations or 

 streams of movement in particular localities at certain times of year. This, however, 

 opens up a more complex field of inquiry which would be rather beyond the scope of the 

 present general discussion. 



As a probable explanation of the grouping of whales in the separate areas Hjort, Lie 

 and Ruud postulated separate cyclonic systems in the hydrological conditions. Deacon's 

 account, however, of the principal hydrological features of the Southern Ocean does not 

 point to any obvious connexion between the current systems and the separate whaling 

 grounds. The distribution of Humpbacks, indeed, strongly suggests that the Antarctic 

 groups, which correspond to the distinct whaling grounds, are dependent rather on the 

 positions of the southern continents than upon hydrological conditions ; and it may be 

 that since Blue and Fin whales tend to concentrate in much the same regions in the 

 Antarctic, they too, although they do not crowd into temperate coastal waters, are still 

 loosely influenced by the southern land-masses, and that it is the subsidiary features of 

 their distribution that are controlled by their immediate environment. 



So far we have considered only the longitudinal distribution of whales in the Southern 

 Ocean, that is to say their distribution and varying abundance in different sectors and 

 between different longitudes. The latitudinal or north-south distribution is closely con- 

 cerned with the hydrological conditions and distribution of pack-ice, and can perhaps 



