ORGANIC E VOL UTION. 5 3 



the American continent being some fifteen times 

 the distance from these islands that they are 

 from one another, emigration to them from the 

 .continent is of much more rare occurrence than 

 emigration from one island to another ; and 

 therefore, as more time for variation is thus 

 allowed, while the differences between the in- 

 habitants of island and island are only specific, 

 the differences between the inhabitants of the 

 islands as a group and the inhabitants of the 

 American continent are very often generic. I 

 may mention, in passing, that it was upon dis- 

 covering these relations in the case of the 

 Galapagos Archipelago, and pondering upon 

 them as " marvellous facts," that Mr. Darwin 

 was first led to entertain the idea that the 

 doctrine of descent might be the grand truth 

 for which the science of the nineteenth century 

 was waiting. 



The evidence from oceanic islands, however, 



