DARWIN'S OWN ACCOUNT 15 



clearly perceived the neighbourhood of America, though the islands were 

 separated by so many miles of ocean from the mainland, and differed much 

 in their geological constitution and climate. Still more surprising was the 

 fact that most of the inhabitants of each separate island in this small 

 archipelago were specifically different, though most closely related to each 

 other. The archipelago, with its innumerable craters and bare streams of 

 lava, appeared to be of recent origin; and thus I fancied myself brought 

 near to the very act of creation. I often asked myself how these many 

 peculiar animals and plants had been produced: the simplest answer 

 seemed to be that the inhabitants of the several islands had descended 

 from each other, undergoing modification in the course of their descent; 

 and that all the inhabitants of the archipelago were descended from those 

 of the nearest land, namely America, whence colonists would naturally 

 have been derived. But it long remained to me an inexplicable problem 

 how the necessary degree of modification could have been effected, and it 

 would have thus remained for ever, had I not studied domestic productions, 

 and thus acquired a just idea of the power of Selection. As soon as I had 

 fully realized this idea, I saw, on reading Malthus on Population, that 

 Natural Selection was the inevitable result of the rapid increase of all 

 organic beings; for I was prepared to appreciate the struggle for existence 

 by having long studied the habits of animals. 



Before visiting the Galapagos I had collected many animals whilst 

 travelling from north to south on both sides of America, and everywhere, 

 under conditions of hfe as different as it is possible to conceive, American 

 forms were met with — species replacing species of the same peculiar 

 genera. Thus it was when the Cordilleras were ascended, or the thick 

 tropical forests penetrated, or the fresh waters of America searched. Sub- 

 sequently I visited other countries, which in all their conditions of life were 

 incomparably more like parts of South America, than the different parts 

 of that continent are to each other; yet in these countries, as in Australia 

 or Southern Africa, the traveller cannot fail to be struck with the entire 

 difference of their productions. Again the reflection was forced on me 

 that community of descent from the early inhabitants of South America 

 would alone explain the wide prevalence of American types tlu-oughout 

 that immense area. 



To exhume with one's own hands the bones of extinct and gigantic 

 quadrupeds, brings the whole question of the succession of species vividly 

 before one's mind; and I found in South America great pieces of tesselated 

 armour exactly like, but on a magnificent scale, that covering the pigmy 

 armadillo; I had found great teeth like those of the living sloth, and bones 

 like those of the cavy. An analogous succession of allied forms had been 

 previously observed in Australia. Here then we see the prevalence, as if 

 by descent, in time as in space, of the same types in the same areas; and 

 in neither case does the similarity of the conditions by any means seem 

 sufficient to account for the similarity of the forms of life. It is notorious 

 that the fossil remains of closely consecutive formations are closely allied 

 in structure, and we can at once understand the fact if they are closely 

 allied by descent. The succession of the many distinct species of the same 



