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The Museum Gazette 



quite as probable that the impetus of migration towards this 

 lost continent should be retained as that a dog should turn 

 round before lying down on a rug, merely because his 

 ancestors found it necessary thus to hollow out a couch in 

 the long grass." Other writers, however, discredit the 

 " Atlantis" theory, and hold that diminished food supplies 

 bring about the migration in the case of this little mammal, 

 a view which receives support from the fact that the incur- 

 sions are never regular, as in the case of the swallow and 

 other migratory birds. 



Certain fishes are regular migrants. With them the move- 

 ments are generally connected with spawning ; for example, 

 many members of the herring tribe (Clupeida) move into 

 shallow, and consequently warmer, water, in spring, prior to 

 depositing their ova. 



For the same cause some reptiles and crustaceans migrate, 

 e.g., the violet landcrab of the West Indies, which lives many 

 miles inland, makes an excursion once a year to the sea to 

 deposit its spawn. In this country it has been observed that 

 toads have their favourite breeding-ponds, and probably travel 

 considerable distances to gain them. 



Judging from geological evidence, the migration trait with 

 mammals is of very remote origin. The Camelidce, now con- 

 fined to South America and Asia, are an American group ; 

 their remains occur in the Miocene beds of North America, 

 from which region the true camels migrated into Asia, and 

 the llamas into South America. 



Amongst invertebrates we find no regular migration on a 

 large scale. The nearest approach to it are the remarkable 

 movements of certain butterflies across the Isthmus of 

 Panama towards the sea in midsummer, many years in suc- 

 cession. Similar flights have been observed in Ceylon. The 

 destination of the insects is not known. 



Some geologists maintain that migration existed in the 

 more remote geological periods ; for example, Barraude con- 

 cludes that this trait was established amongst the Trilobites, 



