2O2 



EVOLUTION OF TO-DAY. 



country to another. Australia and America are 

 becoming filled with European species, and Europe 

 is also receiving many American forms. Barriers no 

 longer exist, and it will require only a few more cen- 

 turies to modify the distribution of animals to such 

 an extent that the rules which are now found will 

 have more exceptions than cases of agreement. 



