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 gencral 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, 
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