274 THE SURVIVAL OF THE UNLIKE. [XV. 



respecting this wonderful history has served strangely 

 to change some of our preconceived ideas. We must 

 now be prepared to admit that an Eden can be 

 planted even in Spitzbergen, that there are possibili- 

 ties in this old earth of ours which its present con- 

 dition does not reveal to us ; that the present state 

 of the world is by no means the best possible in 

 relation to climate and vegetation ; that there have 

 been and might be again conditions which could con- 

 vert the ice -clad arctic regions into blooming para- 

 dises, and which at the same time would moderate 

 the fervent heat of the tropics. We are accustomed 

 to say that nothing is impossible with God ; but how 

 little have we known of the gigantic possibilities 

 which lie hidden under some of the most common of 

 his natural laws ! ' ' 



All these considerations go to establish three gen- 

 eral laws : 1 . That distribution of plants and ani - 

 mals is determined largely by climatic and other 

 physical causes. 2. That species have a local or 

 single origin. 3. That the origin of our present 

 temperate flora is in the north. These generalizations 

 were written before Darwin's theories appeared, and 

 before Heer had published the fossil histories of the 

 arctic regions, and they at once establish Gray's place 

 amongst philosophical naturalists. 



We have now observed that the very facts which 

 led Schouw, De Candolle, and others to accept an 

 hypothesis of the multiple origin of species are the 

 ones which chiefly explain and prove the conclusions 

 of Gray. In the vicissitudes of geologic time, plants 

 retreated up the mountains or persisted along the cold 

 shores of the northern lakes, giving rise to the curious 



