200 SPECIES NOT 



modified condition. These emigrants mingled with 

 the inhabitants of the Old and New World, 

 and had thus to complete the productions of two 

 other great regions, which was of course favour- 

 able to the theory of modification with descent. 

 Mr. Darwin says that the cases of relationship 

 without identity, thus produced, are inexplicable 

 on' the theory of creation. It strikes me that 

 the explanation of Dr. Asa Gray will be accepted 

 by nine people out of ten in preference to that 

 of Mr. Darwin. 



Now with regard to the geographical distribu- 

 tion of animals. Suppose, as suggested by 

 Agassiz, a traveller were to embark at Iceland, 

 and pass through the continent of America. lie 

 would go through representatives of every cli- 

 mate in the world. In Greenland and Baffin's 

 Bay the fauna will be arctic, and for the most 

 part identical with that of the same region in 

 Europe. When he reaches Newfoundland he will 

 find forests succeed the wide and naked turf 

 of the plains, and animals appropriate thereto. 

 This would be the commencement of the tem- 

 perate fauna. As he advances to New England 

 and Nova Scotia, species gradually increase in 

 number, until he arrives amid the rich, and as- 

 tonishingly various, animals of the tropics. Going 

 on towards the tropic of Capricorn, the contrast 

 of the season will be more marked, the vegetation 

 less luxuriant, and the animals will become fewer 

 and less varied. He is now again in the tem- 

 perate zone, and, as he approaches Cape Horn, 



