Ixxviii 



THE PROCESS OF DISPERSAL. 



in Scotland, facts regarding which, I claim, are fully substantiated ; 

 and I ask, how otherwise can such sudden change be accounted for? 

 I have been answered, privately, by the apparently simple counter- 

 statement that tliis was all due to the natural increase and congestion 

 of the species in question at further north sites. 



Very good; I accept that, but scarcely as a mere alternative. 

 Eather would I assign it to direct cause and effect, and not accept 

 them as separate factors. Congestion way have taken place, I 

 grant; but all the more therefore, I think, would an overflow be 

 likely to take place along those lines which would offer the least 

 resistance, whether purely from temperatural causes, or from these 

 and others combined. 



If this view be adopted, how many other species might — or might 

 not — be similarly affected, or affected similarly on perhaps slightly 

 divergent issues ? I believe I have evidence of many more. 



Whether these views may gain acceptance I do not know ; but 

 I would ask that more attention be paid to them by field-observers, 

 and may I hope, from our meteorological offices ; and that they may 

 even obtain some little appreciation from our museum authorities, 

 who are endeavouring to locate the birthplaces of innumerable 

 varieties or " sub-species," by a study of the vast accumulations of 

 correctly authenticated specimens under their charge. 



It appears to me to be a pity — I hope I may be misinformed — 

 that dry- and luet-hulb records do not yet attain to a place amongst 

 the true sciences unless they are accompanied by other outdoor 

 and parallel observations. I think this has been greatly neglected 

 in the past by our expensive meteorological societies — at least so 

 far as any systematised effort has been made. Such absence of 

 systematised effort in the past seems to have rendered any beginning 

 in inquiries regarding migration and dispersal and distribution of life 

 a great deal more difficult than it might have been. But — as the 

 saying is — there is little good to be found in crying over spilt milk 

 (and money) now. Many individual efforts have been made, but 

 these have almost always been sporadic or interrupted, and no attempt 

 — with any success — has been inaugurated and carried out by which 

 systematic work could be overtaken by our meteorological associa- 

 tions as a whole. When saying this, I distinctly refer to our British 

 meteorological institutions, and I judge, in saying so, from an apparent 



