CENTRES OF SUPPOSED CREATION 401 



broken interspaces. The great and striking influence of bar- 

 riers 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 con- 

 fined 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 pre- 

 vail, 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 

 area alone, and having subsequently migrated from that area 

 as far as its powers of migration and subsistence under past 

 and present conditions permitted, is the most probable. Un- 

 doubtedly many cases occur, in which we cannot explain how 

 the same species could have passed from one point to the 

 other. But the geographical and climatal changes which 

 have certainly occurred within recent geological times, must 

 have rendered discontinuous the formerly continuous range 

 of many species. So that we are reduced to consider whether 

 the exceptions to continuity of range are so numerous and 

 of so grave a nature, that we ought to give up the belief, 

 rendered probable by general considerations, that each species 

 has been produced within one area, and has migrated thence 

 as far as it could. It would be hopelessly tedious to discuss 

 all the exceptional cases of the same species, now living at 

 distant and separated points, nor do I for a moment pretend 

 that any explanation could be offered of many instances. 

 But, after some preliminary remarks, I will discuss a few of 

 the most striking classes of facts; namely, the existence of 

 the same species on the summits of distant mountain ranges, 

 and at distant points in the arctic and antarctic regions; and 

 secondly (in the following chapter), the wide distribution of 

 fresh-water productions; and thirdly, the occurrence of the 



