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 consistently 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 — everywhere 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 



