242 Darwin, and after Darwin. 
plain why some of the Alpine species are unique, 
though closely allied to Arctic forms. 
Next we saw that, although living things are always 
adapted to the climates under which they live (since 
otherwise they could not live there at all), it is equally 
true that, as a rule, besides the area on which they do 
live, there are many other areas in different parts of 
the globe where they might have lived equally well. 
Consequently we must conclude that, if all species 
were separately created, many species were severally 
created on only one among a number of areas where 
they might equally well have thrived. Now, although 
this conclusion in itsclf may not seem opposed to the 
theory of special creation, a most serious difficulty is 
raised when it is taken in connexion with another fact 
of an equally general kind. This is, that on every 
biological region we encounter chains of allied species 
constituting allied genera, families, and so on; while 
we scarcely ever meet with allied species in different 
biological regions, notwithstanding that their climates 
may be similar, and, consequently, just as well suited 
to maintain some of the allied species. Hence we 
must further conclude, if all species were separately 
created, that in the work of creation some unac- 
countable regard was paid to making areas of dis- 
tribution correspond to degrees of structural affinity. 
A great many species of the rat genus were created 
in the Old World, and a great many species of 
another, though allied, genus were created in the 
New World: yet no reason can be assigned why no 
one species of the Old World series should not just 
as well have been deposited in the New World, and 
vice versa. On the other hand, the theory of evolution 
