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EEFEEENCE TO THE OEIGIN OF SPECIES 



415 



Dowliere else in tlie world. Out of twentj-six species all but 

 three or four are peculiar to these islands, at the same time 



are of South American types. What 



them 



is still more worthy of note, several of these land-birds are 

 peculiar to a single island of the group.* To explain this 

 we may suppose that continuous gales have rarely blown 



'om 



South America to the Galapagos since these islands 

 first lifted their heads above the waves, and for this reason 

 stragglers have only arrived after long intervals, some on 

 one island, and some on another. Once established, they 

 have remained isolated, without communication with birds 

 of the parent stock on the South American mainland, or with 

 settlers of the same stock on other parts of the archipelago. 



On this 



Mr. Godman 



remai 



while in the 



Azores, winds are constantly blowing from all points of 

 the compass so that land-birds are carried during storms 

 from one island to another, in the Galapagos there are no 

 such violent gales, but usually nninterrupted calms. He 

 also adds, that while the marine currents in the Azores flow 

 in varying directions, those of the Galapagos are strong, 



direction. As to the web-footed 



same 



and always in the 

 birds or waders of the 



Mr 



common 



to the nearest continent.f This fact agrees well with the 

 very wide range of this order of birds in all parts of the 

 world, and is in accordance with their migratory habits. 

 The relationship of the birds of the Atlantic islands to 



"North 



ally 



m a 



tional 



continuous continent. A few excep- 



IN^atural 



may 



some cases have arisen 



them may perhaps be the descendants of Miocene 



tinent. 



mother 



Insects. — The 



Madeira 



Salvages, and the 



Canaries, unlike the birds, exhibit a large proportion of 



many 



^ 



Darwin, Origin of Specicfe, p. 465. 



t Ibid. 



