Clare Island Survey — Phanerogamia. 10 95 



Perhaps a nearer parallel to the incoming of the Clare Island flora after the 

 Ice Age, if we accept a Glacial extinction of the flora, may be found in Spitz- 

 bergen ; the results of EkstamV researches there are that he hypothecates 

 a land-bridge to the eastward (as Nathorst 8 did before him), suggesting that a 

 few Scandinavian species which occur on Spitzbergen, but not on Nova 

 Zembla to the eastward, may have been brought direct by birds. 



The whole question of plant-migration across barriers centres round the 

 oft-debated point of the efficacy of " accidental " or " occasional " dispersal : 

 the advocates on the one side taking their stand on the lack of direct evidence 

 and the lack of actual observation of the accomplishment of long distance 

 dispersal by these means ; the other side demanding any other explanation of 

 certain facts of distribution, and pointing out the immense period of time 

 available for colonization by " accident." The older students of distribution, 

 led by Darwin and Wallace, argued that such dispersal must have taken 

 place, calling to witness the fauna and flora of oceanic islands, and pointing 

 out the undeniable wide possibilities. Later naturalists, adhering to Forbes's 

 view that overland migration was the rule, sought for actual instances of 

 over-sea dispersal, but finding none, or next to none, were tempted to condemn 

 the whole " occasional " hypothesis — what was not taking place now did not 

 take place in the past. But, came the reply, we cannot hope to see these 

 things actually happening — to find condensed into the limited period of our 

 own experience what has been spread over tens of thousands of years. 

 Nature, as A. E. Wallace has said, 3 can afford to wait. Man, dressed in a 

 little brief scientific experience, cannot thus discount the influence of the 

 ages. 



In August was the Jackal born ; 



The Rains fell in September ; 

 " Now such a fearful flood as this," 



Said he, " I can't remember ! " 



In the absence of any body of direct evidence, we are driven to an attempt 

 to estimate probabilities ; and here again we are at fault, for we have not the 

 facts and figures which would allow of even an approximate estimate being 

 made. So the question resolves itself into a matter of opinion, based on a 

 general survey of the case ; and from such opinion we cannot eliminate the 

 personal equation. 



But we must remember that there is all the difference in the world 

 between possibilities and probabilities ; and it seems to me that in many 



1 0. Ekstam : Spitzbergen, loc. cit., p. 56. 



2 A. G-. Nathorst : Studien uber die Flora Spitzbergens. Englers Bot. Jahrbiicher, iv, 

 pp. 432-448. 1S83. 



3 Geographical Distribution of Animals, i, p. 32. 



