THE EUROPEAN SEAS. 



125 



wards, seek strata of water of the temperature best 

 suited for them. The waters of the polar current 

 are superficial in this region. The whales feed 

 near the surface, instead of diving down to seek 

 their food, as they do in higher latitudes. Medusae 

 will be borne to lower latitudes in greater abund- 

 ance at one season than at others, according to the 

 variable extension and force of the polar current, 

 and the whales will follow them, changing their 

 haunts accordingly at different seasons. This may 

 to a certain extent be true, but not wholly so ; for 

 in the first place, it is not the whale of the Arctic 

 seas, but the sperm whale, which is present here ; 

 and in the second, the experience of sea-going 

 naturalists is every day proving more and more 

 that Medusas, although free swimmers in the ocean, 

 are as definitely limited in their geographical dis- 

 tribution as more fixed animals ; so that the Me- 

 dusae of the Azores are not likely to come from 

 the north. Indeed this fact seems to have attracted 

 the attention of sailors ; I recollect meeting with 

 a paper in the "Nautical Magazine," in which it 

 was proposed in some circumstances to find the ship's 

 position by means of Medusas. 



The southern limits of the Lusitanian province 

 are extra-European. I had always fancied that the 

 line might be traced at or a little to the north of 

 the Canaries, until Mr. Mac Andrew returned from 

 his cruise to those islands in 1852. The zoological 

 volume of the great work by Webb and Berthelot, 



