124 ISLAND LIFE 



mild climate and luxuriant vegetation of tlie Arctic zone. 

 If -my readers will follow me with the care and attention 

 so difficult and interesting a problem requires and deserves, 

 they will find that I have grappled with all the more im- 

 portant facts which have to be accounted for, and have 

 offered what I believe is the first complete and sufficient 

 explanation of them. The im23ortant influence of climatal 

 changes on the dispersal of animals and plants is a suffi- 

 cient justiiication for introducing such a discussion into 

 the present volume. 



