SINGLE CENTRES OF CREATION. 355 



the simplicity of the view that each species was first pro- 

 duced within a single region captivates the mind. He who 

 rejects it, rejects the vera causa of ordinary generation with 

 subsequent migration, and calls in the agency of a miracle. 

 It is universall)'' admitted, that in most cases the area 

 inhabited 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 incapacit} 1 - 

 of migrating across a wide sea is more clear in the case of 

 terrestrial mammals 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 possessing 

 the same quadrupeds with the rest of Europe, for they were 

 no doubt once united. But if the same species can be pro- 

 duced 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 multi- 

 tude of European animals and plants have become natural- 

 ized 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 interspaces. The 

 great and striking influence of barriers of all kinds, is intel- 

 ligible only on the view that the great majority of species 

 have been produced on one side, and have not been able to 

 migrate to the opposite side. Some few families, many sub- 

 families, very many genera, a still greater number of sections 

 of genera, are confined to a single region ; and it has been 

 observed by several naturalists that the most natural genera, 

 or those genera in which the species are most closely related 

 to each other, are generally confined to the same country, or 

 if they have a wide range that their range is continuous. 

 What a strange anomaly it would be if a directly opposite 

 rule were to prevail when we go down one step lower in the 

 series, namely, to the individuals of the same species, and 

 these had not been, at least at first, confined to some one 

 region ! 



Hence, it seems to me, as it has to many other naturalists, 

 that the view of each species having been produced in one 



