208 Darwin, and after Darwin, 
distribution is not to be regarded as a crucial test 
between the rival theories of creation and evolution 
in all cases indiscriminately, I must next remark that 
it is undoubtedly one of the strongest lines of evidence 
which we possess. When we once remember that, 
according to the general theory of evolution itself, the 
present geographical distribution of plants and animals 
is “the visible outcome or residual product of the 
whole past history of the earth,” and, therefore, that of 
the conditions determining the characters-of life in- 
habiting this and that particular area continuity or 
discontinuity with other areas is but one,—when we 
remember this, we find that no further reservation has 
to be made: all the facts of geographical distribution 
speak with one consent in favour of the naturalistic 
theory. 
The first of these facts which I shall adduce is, that 
although the geographical range of any given species 
is, as a rule, continuous, such is far from being 
always the case. Very many species have more or 
less discontinuous ranges—the mountain-hare, for 
instance, extending from the Arctic regions over the 
greater portion of Europe to the Ural Mountains and 
the Caucasus, and yet over all this enormous tract 
appearing only in isolated or discontinuous patches, 
where there happen to be cither mountain ranges or 
climates cold enough to suit its nature. Now, in all 
such cases of discontinuity in the range of a species 
the theory of evolution has a simple explanation to 
offer—namiely, either that some representatives of the 
species have at some former period been able to 
migrate from one region to the other, or else that at 
