Chap. XI. DURING THE GLACIAL PERIOD. 365 



of transport, immigrants from Europe or any other 

 continent, that a poorly-stocked island, though standing 

 more remote from the mainland, would not receive 

 colonists by similar means. I do not doubt that out of 

 twenty seeds or animals transported to an island, even 

 if far less well-stocked than Britain, scarcely more than 

 one would be so well fitted to its new home, as to 

 become naturalised. But this, as it seems to me, is 

 no valid argument against what would be effected by 

 occasional means of transport, during the long lapse of 

 geological time, whilst an island was being upheaved 

 and formed, and before it had become fully stocked 

 with inhabitants. On almost bare land, with few or no 

 destructive insects or birds living there, nearly every 

 seed, which chanced to arrive, would be sure to germi- 

 nate and survive. 



Dispersal during the Glacial period. — The identity of 

 many plants and animals, on mountain-summits, sepa- 

 rated from each other by hundreds of miles of low- 

 lands, where the Alpine species could not possibly exist, 

 is one of the most striking cases known of the same 

 species living at distant points, without the apparent 

 possibility of their having migrated from one to the 

 other. It is indeed a remarkable fact to see so many 

 of the same plants living on the snowy regions of the 

 Alps or Pyrenees, and in the extreme northern parts 

 of Europe ; but it is far more remarkable, that the 

 plants on the White Mountains, in the United States of 

 America, are all the same with those of Labrador, and 

 nearly all the same, as we hear from Asa Gray, with those 

 on the loftiest mountains of Europe. Even as long ago 

 as 1747, such facts led Gmelin to conclude that the 

 same species must have been independently created at 

 several distinct points; and we might have remained 



