162 WONDERS OF ORGANIC LIFE. 



Much has been written respecting the migra- 

 tion of birds, treating the subject as if the birds 

 themselves reasoned on the necessity of their 

 journey and on the course most advantageous 

 for them to take, as the captain of a vessel 

 bound on the one hand for the high-northern 

 whale-fishery, or on the contrary for Australia 

 or the southern seas, might do, with his chart 

 before him, calculating the effects of currents 

 and trade winds. Herein many persons labour 

 under a singular confusion of ideas ; the end to 

 be answered by the migration of a bird is un- 

 doubtedly its preservation, but the mode of 

 operation is instinctive. The bird knows 

 nothing of north, south, east, or west ; yet as 

 instinct directs it, so it urges its flight, and but 

 for this instinctive impulse it would remain 

 stationary, and in many instances starve. 



So far we have attended only to the instinct- 

 directed migration of birds. But we must not 

 forget that other animals regularly migrate, and 

 here we more particularly allude to the oceanic 

 mammalia. The movements of these, however, 

 as may be easily imagined, are only partially 

 known to us. For example, certain seals in 

 the Arctic regions certainly migrate, while 

 others are stationary, or only perforin a short 

 journey, as circumstances connected with their 

 fishing operations may render convenient. 

 Crantz, in his History of Greenland, notices two 

 species of seal which he considers as decidedly 

 migratory. One he calls Neitersoak, (its Es- 

 quimaux name,) which we take from his 



