MIGRATIONS OF ANIMALS. 



to places more conformable to its own habits and wants. Thus, 

 the migration to and fro fulfils at once the double purpose 'of 

 providing for the preservation of the species and that of the 

 individual. 



33. Where the migration is irregular, and the voyage not 

 long, the movement is prompted by the necessity of seeking a 

 locality where the proper nourishment <)f the animal is more 

 abundant. In such cases, the animal having exhausted the 

 supplies of a particular district, departs in quest of another, 

 and does not voyage further than is necessary for that object. 



Fig. 10. The Mitki. 



34. Whatever be the motive which may prompt such voyages, 

 they are almost invariably preceded by a general meeting, having 

 all the appearance of a concerted one, composed of all the 

 individuals of the species which inhabit the locality where it 

 takes place. When the purpose of the voyage is change of 

 climate, they do not wait until they are driven forth by an undue 



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