164 ZOOLOGICAL GEOGRAPHY. [part ji 



which have been founded on supposed difficulties in the distri- 

 bution of animals in space and time. 



It also illustrates and supports the geological doctrine, of the 

 general permanence of our great continents and oceans, by 

 showing how many facts in the distribution of animals can 

 only be explained and understood on such a supposition ; and 

 it exhibits, in a striking manner, the enormous influence of the 

 Glacial epoch, in determining the existing zoological features of 

 the various continents. 



And, lastly, it furnishes a more consistent and intelligible 

 idea than has yet been reached by any other mode of investiga- 

 tion, of all the more important changes of the earth's surface 

 that have probably occurred during the entire Tertiary period ; 

 and of the influence of these changes, in bringing about the 

 general features, as well as many of the more interesting details 

 and puzzling anomalies, of the Geographical Distribution of 

 Animals- 



