LIST ()!•• AM.MAI.S Ol' ST f 1 ZHKKGEN. 171 



sufficient instinct or power of motion to enable tlieni to retire 

 into a more southern region. Now, such an event is pro- 

 vided against, by the constant prevalence of a current setting 

 towards the south-west, Avhich carries away the ice into a 

 parallel where it can be dissolved, and occasions a circulation 

 of water into the frozen regions from a warmer climate. 

 And this circulation of the water is beautifully accomplished; 

 for, while the superficial current is jierforming its office, in 

 carrying away a portion of ice, an under-current setting to 

 the noi'thward, is acting an equally important ji^^i't in afford- 

 ing warmth to the seas of the higher latitudes, and prevent- 

 ing the too great accumulation of the ice. But how is it, it 

 might be asked, when a current in the waters, inhabited by 

 the minor medusae, is constantly setting to the southward, 

 that these animals are not carried away into a southern re- 

 gion altogether ? This question, if we may be allowed to 

 argue hypothetically, admits of an easy solution. Animals, 

 Ave find, when possessing any power of moving, though they 

 be of the most imperfect kind of organization, generally em- 

 ploy that power by a sort of instinctive faculty, as may best 

 serve the purposes for which they were called into existence. 

 Now, it would be no stretch of commonly received prin- 

 ciples, to suppose, that Avhenever the minor medusas, etc., 

 are carried to a certain extent southward, they may sink in 

 the water as far as the stream of the under-current, and by 

 it be conveyed back again into their proper element. The 

 fact of the olive-green coloured sea Avater maintaining a great 

 similarity of position, for many years together, Avhile surface 

 after surface of ice is carried aAvay by the current and dissi- 

 pated, is in support of this conjecture. Thus, by a most 

 beautiful contrivance, a large portion of tbe surface of the 

 globe is rendered habitable, Avhich Avould otherAvise be a 

 solid mass of ice, and by the Avarmth of the loAver stratum of 

 the Polar Sea it is rendered congenial to many tribes of 

 animals Avhicli must^ othcrAvisc, have incumbered other re- 



