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 snaton- 



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Ch. XLI.] 



EEFERENCE TO THE ORIGIN OF SPECIES. 



417 



by wliicli insects are often carried seaward^ may have been 



means oi introducing 



progenitors of tlie present insular fauna. 



The inferior facilities enjoyed by insects as compared to 

 birds of crossing the sea^ affords probably the true explana- 



marked 



mother 



tively small number of insects common to different islands of 



group. In proportion as the interchange of species 



same 



Natural 



tion will be efficacious in forming distinct races in separate 



islands. 



examination 



by Mr. Godman^ and described by Mr. Crotch^"^ shows that 

 that archipelago presents the same phenomena as the Ca- 



although the proportion of Atlantic 

 the liyingr European forms more Dre- 



Madeiras 



dominant. 

 Plants.- 



Hooker^ in his admirable essay on Insular 



t remarks that in Madeira 



man 



poppies, fumitories, groundsels, and other weeds which he 

 has brought with him unintentionally, there are other native 

 varieties of European species, and sometimes representative 

 genera, which indicate a relationship to the nearest continent. 

 He also observes that whereas we find on ascending moun- 

 tains in Great Britain or on the continent of Europe, from 

 the height of 2,000 feet and upwards, species proper to more 

 northern latitudes, and differing from those flourishing at 



Madeira 



6,000. [ 



meet 



that to 



become 



same 



tions. Had 



mi 



Glacial period. 



from higher latitudes during 



* Azorean Coleoptera, Zool. Proc 

 1867; pt. ii. p. 359. 



VOL. II. 



t Lecture to Brit. Assoc. Notting- 

 ham, 1866 ; Gardener's Chronicle, 1867. 



E E 



