RECAPITUL-\TION' AN'D CONCLUSION 517 



eties 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 source whence im- 

 migrants might have derived. We see this in the striking 

 relation of nearly all the plants and animals of the Gala- 

 pagos archipelago, of Juan Fernandez, and of the other 

 American islands, to the plants and animals of the nei^- 

 bouring American mainland; and of those of the Cape de 

 Verde archipelago, 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 or- 

 ganic 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 ex- 

 tinction and divergence of character. On these same prin- 

 ciples 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 are far more serviceable than others 

 for classification; — why adaptive characters, though of para- 

 mount importance to the beings, are of hardly any impor- 

 tance in classification; why characters derived from rudi- 

 mentary parts, though of no service to the beings, are often 

 of high classificatory value ; and why embryological charac- 

 ters are often the most valuable of all. The real aflBnities 

 of all organic beings, in contradistinction to their adaptive 

 resem.blances, are due to inheritance or community of de- 

 scent. The Natural System is a genealogical arrangement, 

 with the acquired grades of difference, marked by the terms, 

 varieties, species, genera, families. &c. : and we have to dis- 

 cover the lines of descent by the most permanent characters 

 whatever they may be and of however slight vital impor- 

 tance. 



The similar framework of bones in the hand of a man, 

 wing of a bat, fin of a porpoise, and leg of the horse. — the 

 same ntmiber of vertebrae forming the neck of the giraffe 

 and of the elephant. — and innumerable other such facts, at 

 once explain themselves on the theorv* of descent with slow 

 and slight successive modifications. The similarity of pat- 



