290 EECAPITULATION. [Chap. XV. 



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 

 creationj 



The existence of closely allied or representative species 

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

 modification, that the same parent-forms formerly in- 

 habited both areas : and we almost invariably find that 

 wherever many closely allied species inhabit two areas, 

 some identical species are still common toboth. Wherever 

 many closely allied yet distinct species occur, doubtful 

 forms and varieties belonging to the same groups like- 

 wise occur. It is a rule of high generality that the in- 

 habitants of each area are related to the inhabitants of 

 the nearest source 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 

 groux^s 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 we see how it is, that the 

 mutual affinities of the forms within each class are so 

 complex and circuitous. We see why certain characters 



