NATURAL SELECTION. 11 



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 he 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 throughout 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 succes- 

 sion 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 

 genus throughout the long series of geological formations 

 seems to have been unbroken or continuous. New species 

 come in gradually one by one. Ancient and extinct forms of 

 life are often intermediate in character, like the words of a 

 dead language with respect to its several offshoots or living 

 tongues. All these facts seemed to me to point to descent 

 with modification as the means of production of new 

 species. 



The innumerable past and present inhabitants of the 

 world are connected together by the most singular and 

 complex affinities, and can be classed in groups under groups, 

 in the same manner as varieties can be classed under species 

 and sub-varieties under varieties, but with much higher 

 grades of difference. These complex affinities and the rules' 



