PENDULATION THEORY 435 



pense with land connections, and he rejects the theories of 

 accidental dispersal as quite inapplicable to the solution of the 

 antarctic biological problems. For my own part, I think that 

 changes of land and water, combined with warm currents in 

 the Polar regions, would likewise explain the same phenomena 

 in a satisfactory manner, and I prefer to adopt the latter view 

 until we possess more definite information as to evidence on 

 which the pendulation theory is founded. 



I have endeavoured in this work to show how the gradual 

 evolution of our continents and the former changes of land 

 and water can be demonstrated by a study of the geographical 

 distribution of living animals and plants. Whenever possible 

 I have taken advantage of our palaeontological and geological 

 knowledge in furtherance of this object, and I venture to 

 think that I have succeeded in unravelling some intricate 

 problems of the palaeogeography of America. Indirectly I 

 have thus been able to indicate the manner in .which North 

 and South America became populated, and the extent to 

 which these continents took part in supplying animals and 

 plants to other regions of the world. 



