CH. II PERMANENCE OF THE GREAT OCEANIC BASINS 29 



lastly, that the great oceanic and continental areas have 

 never changed places " ; and, in the summary of the whole 

 work, he says : " The occupation of an entire hemisphere 

 by one gi'eat ocean is a remarkable circumstance, and we 

 have seen reason for believing that this is a very ancient 

 division of the surface, and that it is probably a mistake 

 to suppose that every part of it has been sometimes raised 

 above the sea, and sometimes depressed beneath it. The 

 truth seems to be, that the region subject to these altera- 

 tions of conditions does not extend very far away from the 

 present coast lines." 



When studying the causes which have brought about 

 the geographical distribution of animals, I was compelled 

 to deal with this question, because I found that it had 

 been the custom of many writers to solve all anomalies of 

 distribution by the creation of hypothetical lands, bridg- 

 ing across the great oceans in various directions and at 

 many different epochs ; and, having arrived at the con- 

 clusion that the distribution of organisms could be more 

 harmoniously and consistently explained without such 

 changes of sea and land, which usually created greater 

 difficulties than those they were intended to explain, I 

 gave, in my Idand Life, a brief statement of the evi- 

 dence which appeared to me to render such changes 

 exceedingly improbable. This evidence was mainly a 

 summary of the facts and arguments adduced by the emi- 

 nent men referred to above, and to this I added in my 

 Darwinism a difficulty founded on mechanical consider- 

 ations which seemed to me to furnish a preliminary reason 

 why we should not accept the doctrine of the interchange 

 of continental and oceanic areas without very clear and 

 cogent reasons. Since then some other arguments of this 

 nature have occurred to me, and as the theory of perman- 

 ence has been recently attacked, by Mr. W. T. Blanford in 

 his presidential address to the Geological Society in 1890, 

 and by Mr. Jukes-Browne in his " Building of the British 

 Isles," it may be as well to consider these difficulties, 

 which suggest, in my opinion, a very powerful argument 

 against the interchange of oceanic and continental areas, 

 and one which has the advantage of not requiring any 



