"52 



BOUNDARY OF THE INDLVN ' 



[Ch. XXXVIII. 



om swimmin 



shore to sliore. 



To assist IIS in accounting; for the marked separation 

 between the Indian and Australian faunas^ as well as for 

 many partial exceptions to the distinctness of the two 

 gronps of animals in some of the islands of the Malay 



archipelago, Mr. Wallace has 



suggested 



an imaginary 



parallel, of which I can only give a brief outline. Suppose 

 the bed of the Atlantic to be gradually converted into land, 

 partly by the deposition of large bodies of sediment poured 

 down by rivers, and partly by slow upheaval and volcanic 

 action. Let the two continents of Africa and America be 

 thus more and more extended, so that the ocean, which now 

 separates them, should at last be reduced to an arm of the 

 sea a few hundred miles wide. Let us, at the same time, 

 imairine several islands to be upheaved in mid-channel, and 

 that, while the subterranean forces varied in intensity and 

 shifted their points of greatest action, these islands became 



mam 



sometimes 



Two 



or more of the islands also might occasionally be joined to- 

 gether and then broken up again, till at last, after many ages 

 of such intermittent action, with many a long intervening 

 period of comparative tranquillity, we might have an irre- 

 gular archipelago of islands filling up the ocean channel of 

 the Atlantic, in whose appearance and arrangement we could 

 discover nothing to tell us which had been connected with 



Amer 



animals 



inhabiting these islands would certainly reveal this portion of 

 their former history. On those islands which had ever formed 

 a part of the South American continent we should be certain 

 to find such common birds, as chatterers, toucans, macaws, 



hummin 



& 



pumas 



on the 



'om 



should be equally sure to meet with horn-bills, orioles, and 

 honey suckers, and some quadrupeds contrasting strongly 

 with those of South America, such as baboons, lions, ele- 

 phants, buffaloes, and giraffes. Those intermediate islands 



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