The Origin of Species 



of descent better fitted for new and degraded 

 habits of life. Lastly, the wonderful law of the 

 long endurance of allied forms on the same con- 

 tinent — of marsupials [as kangaroos] in Australia, 

 of edentata [as armadilloes, sloths, and ant- 

 eaters] in America, and other such cases — is 

 intelligible, for within the same country the exist- 

 ing and the extinct will be closely allied by 

 descent. 



Looking to geographical distribution, if we 

 admit that there has been during the long course 

 of ages much migration from one part of the world 

 to another, owing to former climatical and 

 geographical changes and to the many occasional 

 and unknown means of dispersal, then we can 

 understand, on the theory of descent with modi- 

 fication, most of the great leading facts in dis- 

 tribution. We can see why there should be so 

 striking a parallelism in the distribution of or- 

 ganic beings throughout space, and in their 

 geological succession throughout time ; for in both 

 cases the beings have been connected by the bond 

 of ordinary generation, and the means of modifi- 

 cation have been the same. We see the full 

 meaning of the wonderful fact, which has struck 

 every traveller, namely, that on the same con- 

 tinent, under the most diverse conditions, under 

 heat and cold, on mountain and lowland, on 

 deserts and marshes, most of the inhabitants 

 within each great class are plainly related; for 

 they are the descendants of the same progenitors 

 and early colonists. On this same principle 

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