CiiAi-. XIV EECAPITULATION. 497 



clearly sec why species belonging to those groups of animals 

 which cannot cross wide spaces of the ocean, as frogs and ter- 

 restrial niumnials, do not inhabit oceanic islands ; and wliy, on 

 the' other hand, new and peculiar species of bats,, animals 

 wliich can traverse the ocean, are so often found on islands far 

 distant from any contni(?nt. Such cases as the presence of pe- 

 culiar 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 existence of closely-allied or representative species in 

 any two areas, implies, on the theory of descent with modifica- 

 tion, 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 conunon to both. Wherever many closely-allied yet 

 distinct species occur, doubtful forms and varieties belonging 

 to the same groups likewise occur. It is a rule of high gener- 

 ality that the inhabitants of each area are related to the inhabi- 

 tants of the nearest source whence innnigrants might have 

 been derived. We see this in the striking relation uf 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 neighboring American main-land ; and 

 of those of the Cape de Verde archipelago and of the other 

 African islands to the African main-land. It must be admitted 

 that these facts receive no explanation on the theory of crea- 

 tion. 



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

 ic beings can be arranged within a few great classes, in groups 

 subordinate to groups, and with the extinct groups often fall- 

 ing in between the recent groups, is intelligible on the tlieory 

 of natural selection with its contingencies of extinction and 

 divergence of character. On these same princijilcs we see how 

 it is that the mutual affinities of the forms Avithin each class 

 are so complex and circuitous. We see why cert^iin charac- 

 ters are far more seniceable than others fur classification — 

 why adaptive characters, though of paramount imjiortance to 

 the beings, are of hardly any importance in classification ; 

 why characters derived from rudimentary parts, though of no 

 service to the beings, are often of high classiiicatory value; 

 and why embryological charactei-s are often the most valuable 

 of all. The real affinities of all organic beings, in contradis- 

 tinction to tiieir adaptive resemblances, are due to inheritance 



