114 DARWINISM STATED BY DARWIN HIMSELF. 



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 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 naturalized in America and Aus- 

 tralia ; 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 mi- 

 grated across the wide and broken interspaces. The 

 great and striking influence of barriers of all kinds is 

 intelligible 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, and 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 natu- 

 ralists, that the view of each species having been produced 

 in one area alone, and having subsequently migrated from 

 that area as far as its powers of migration and subsistence 



