GEOGRAPHICAL DISTRIBUTION. 109 



they are smaller, and an unusually hot summer 

 in England may similarly reduce the size of 

 insects. The European Urus was much larger 

 than the Indian Gaur or Gayal. 



The islands of the Galapagos Archipelago, off 

 South America, produce many species of animals 

 and plants which are unknown on the mainland, 

 though all belong to American types ; but it is 

 much more remarkable that each island is 

 inhabited by different, though allied, species. 

 The insects of Corsica and Sardinia differ 

 widely from those of the mainland ; and many 

 species which occur commonly from Britain to 

 Japan or California, differ less at the extre- 

 mities of their range, than do their Corsican 

 representatives from Italian specimens. That 

 this variation is chiefly due to long-continued 

 isolation is shown by the occurrence of 

 various intermediate forms in Sicily, which has 

 not been separated from the mainland so 

 long. 



If we believe in the doctrine of Special 

 Creation, it follows that although many species 

 have been created to range over enormous 

 tracts of country, yet the existence of a deep 

 sea between two islands, or between an island 



