290 RECAPITULATION. [Chap. XV 



tant from any continent. Such cases as the presence of 

 peculiar species of bats on oceanic islands and the ab- 

 sence of all other terrestrial mammals, are facts utterly 

 inexplicable on the theory of independent acts of crea- 

 tion. 



The existence of closely allied or representative spe- 

 cies in any two areas, implies, on the theory of descent 

 with modification, that the same parent-forms formerly 

 inhabited both areas; and we almost invariably find that 

 wherever many closely allied species inhabit two areas, 

 some identical species are still common to both. Where- 

 ever many closely alHed yet distinct species occur, doubt- 

 ful forms and varieties belonging to the same groups 

 likewise occur. It is a rule of high generality that the 

 inhabitants of each area are related to the inhabitants of 

 the nearest soui^ce whence immigrants might have been 

 derived. "We see this in the striking relation of nearly 

 all the plants and animals of the Galapagos archipelago, 

 of Juan Fernandez, and of the other American islands, 

 to the plants and animals of the neighbouring American 

 mainland; and of those of the Cape de Verde archi- 

 pelago, and of the other African islands to the African 

 mainland. It must be admitted that these facts receive 

 no explanation on the theory of creation. 



The fact, as we have seen, that all past and present 

 organic beings can be arranged within a few great classes, 

 in groups subordinate to groups, and with the extinct 

 groups often falling in between the recent groups, is 

 intelligible on the theory of natural selection with its 

 contingencies of extinction and divergence of character. 

 On these same principles vfe see how it is, that the mu- 

 tual affinities of the forms within each class are so com- 

 plex and circuitous. We see why certain characters 



