138 SINGLE CENTRES OF CREATION. [Chap. XII. 



difficulty in understanding how the same species could 

 possibly have migrated from some one point to the 

 several distant and isolated points, where now found. 

 Nevertheless the simplicity of the view that each 

 species was first produced within a single region cap- 

 tivates the mind. He who rejects it, rejects the vera 

 causa of ordinary generation with subsequent migra- 

 tion, and calls in the agency of a miracle. It is 

 universally admitted, that in most cases the area in- 

 habited by a species is continuous ; and that when a 

 plant or animal inhabits two points so distant from 

 each other, or with an interval of such a nature, that 

 the space could not have been easily passed over by 

 migration, the fact is given as something remarkable 

 and exceptional. The incapacity of migrating across a 

 wide sea is more clear in the case of terrestrial mam- 

 mals than perhaps with any other organic beings ; and, 

 accordingly, we find no inexplicable instances of the 

 same mammals inhabiting distant points of the world. 

 No geologist feels any difficulty in Great Britain pos- 

 sessing the same quadrupeds with the rest of Europe, 

 for they were no doubt once united. But if the same 

 species can be produced at two- separate points, why do 

 we not find a single mammal common to Europe and 

 Australia or South America ? The conditions of life 

 are nearly the same, so that a multitude of European 

 animals and plants have become naturalised in America 

 and Australia; and some of the aboriginal plants are 

 identically the same at these distant points of the 

 northern and southern hemispheres ? The answer, as 

 I believe, is, that mammals have not been able to 

 migrate, whereas some plants, from their varied means 

 of dispersal, have migrated across the wide and broken 



