RECAPITULATION 299 



and the close alliance of many others, on the most dis- 

 tant mountains, and in the northern and southern tem- 

 perate zones; and likewise the close alliance of some of 

 the inhabitants of the sea in the northern and southern 

 temperate latitudes, though separated by the whole in- 

 tertropical ocean. _AItliough two countries may present 

 physical conditions as closely similar as the same species 

 ever require, we need feel no surprise at their inhabitants 

 being widely different, if they have been for a long 

 period completely sundered from each other; for as the 

 relation of organism to organism is the most important of 

 all relations, and as the two countries will have received 

 colonists at various periods and in different proportions, 

 from some other country or from each other, the course 

 of modiiication in the two areas will inevitably have 

 been different. 



On the view of migration, with subsequent modifica- 

 tion, we see why oceanic islands are inhabited by only 

 few species, but of these, why many are peculiar or en- 

 demic forms. We clearly see why species belonging to 

 those groups of animals which cannot cross wide spaces 

 of the ocean, as frogs and terrestrial mammals, do not 

 inhabit oceanic islands; and why, on the other hand, new 

 and peculiar species of bats, animals which can traverse 

 the ocean, are often found on islands far distant from 

 any continent. Such cases as the presence of peculiar 

 species of bats on oceanic islands and the absence of all 

 other terrestrial mammals are facts utterly inexplicable 

 on the theory of independent acts of creation. 



The exis tenc^ _of-closely allied or representative species 

 in any .two_areas,_iniplies, on the theory of descent with 

 modification, that the same parent- forms formerly inhab- 



