Geographical Distribution. 243 



may claim as direct evidence in its support all the 

 innumerable cases such as these — cases, indeed, so 

 innumerable that, as Mr. Wallace remarks, it may 

 be taken as a law of nature that " every species has 

 come into existence coincident both in space and 

 time with a pre-existing and closely allied species." 

 A general law which, while in itself most strongly 

 suggestive of evolution, is surely impossible to 

 reconcile with any reasonable theory of special 

 creation. Furthermore, this law extends backwards 

 through all geological time with the result that the 

 extinct species, which now occur .only as fossils on 

 any given geological area, resemble the species still 

 living upon that area, as we should expect that they 

 must, if the former were the natural progenitors of 

 the latter. On the other hand, if they were not the 

 natural progenitors, but all the species, both living 

 and extinct, were the supernatural and therefore in- 

 dependent creations which the rival theory would 

 suppose, then no reason can be given why the extinct 

 species should thus resemble the living — any more 

 than why the living species should resemble one 

 another. For, as we have seen, there are almost 

 always many other habitats on other parts of the 

 globe, where any members of any given group of 

 species might equally well have been deposited ; 

 and this, of course, applies to geological no less than 

 to historical time. Yet throughout all time we meet 

 with this most suggestive correlation between con- 

 tinuity of a geographical area and structural affinity 

 between the forms of life which have lived, or are still 

 living, upon that area. 



Similarly, we find the further, and no less suggestive, 



R 2 



