Geographical Distribution. 247 
faunas, and the degree of their affinity—a relation 
which is quite inexplicable on the theory of inde- 
pendent acts of creation.” 
Looking to all these general principles of geo- 
graphical distribution, and remembering the sundry 
points of smaller detail relating to oceanic islands 
which I will not wait to recapitulate, to my mind it 
seems that there is no escape from the following 
conclusion, with which I will bring my brief epitome 
of the evidence to a close. The conclusion to which, 
I submit, all the evidence leads is, that if the doctrine 
of special creation is taken to be true, then it must 
be further taken that the one and only principle 
which has been consistenily followed in the geo- 
graphical deposition of species, is that of so de- 
positing them as to make it everywhere appear that 
they were not thus deposited at all, but came into 
existence where they now occur by way of genetic 
descent with perpetual migration and correlative 
modification. On no other principle. so far as I 
can see, would it be possible to account for the fact 
that “every species has come into existence coincident 
both in space and time with a pre-existing and closely 
allied species,” together with the carefully graduated 
regard to physical barriers which the Creator must 
have displayed while depositing his newly formed 
species on either sides of them—ceverywhere making 
degrees of structural affinity correspond to degrees of 
geographical continuity, and degrees of structural differ- 
ence correspond to degrees of geographical separation, 
whether by mountain-chains in the case of fresh-water 
faunas, by land and by deep sea in the case of marine 
