128 STUDIES IN LIFE AND SENSE. 



part of the old birds to cause them to leave their native area once 

 again, and this time as willing emigrants. Not less strong would be 

 the instinct of the young brought up in the north, and thus with the 

 returning season of spring the birds would fly northwards, and repeat 

 the procedure of the previous year. Admitting these circumstances 

 and the undeniable force of habit, the theory that migration is the 

 strengthening of a chance and favourable association with a new 

 land becomes of likely and feasible kind. That young birds which 

 have never migrated participate by nature and instinct in the migratory 

 tendencies of their parents is proved by one of the most extraordi- 

 nary facts already mentioned in connection with this subject namely, 

 that caged birds of a migratory species become restless, flap their 

 wings against the cage, and exhibit every sign of excitement at the 

 time when their free neighbours are flying homewards. And this 

 being so, the idea that the instinct of the first emigrants of a species 

 would be sufficient to guide them to their new home after a sojourn 

 in the native area of their species, is rendered by no means im- 

 probable. 



The migrations of animals is thus seen to be a subject which 

 relates itself to the geographical distribution of living beings on the 

 one hand, and to the geological or past history of our globe on the 

 other. It also concerns the acquirement of new habits, and the modifi- 

 cation of the old habits of a species, and is thus calculated to teach us 

 some valuable truths concerning the modification of the ways of life 

 at large. To the more evident bearings of the subject on the 

 geographical distribution of animals and on geological change we 

 will return in a succeeding chapter. The present topic is, however, 

 not the least worthy or interesting of the lessons regarding our 

 universe which Nature, from her outspread pages, is continually 

 inviting us to peruse. 



