NATUEAL SELECTION. 11 



gigantic quadrupeds brings the whole question of the succession 

 of species vividly before one's mind ; and I had 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 simi- 

 larity 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 likewise 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 often show combined or 

 intermediate characters, like the words of a dead language with 

 respect to its several offshoots or living tongues. All these 

 and other such facts seemed to me to point to descent with 

 modification as the method of production of new groups of 

 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. It will be seen in my third work that these 

 complex affinities and the rules for classification receive a 

 rational explanation on the principle of descent, together with 

 modifications acquired through natural selection, entailing diver- 

 gence of character and the extinction of intermediate forms. 

 How inexplicable is the similar pattern of the hand of a 

 man, the foot of a dog, the wing of a bat, the flipper of 

 a seal, on the doctrine of independent acts of creation ! how 

 simply explained on the principle of the natural selection of 

 successive slight variations in the diverging descendants from 



