204 THE entomologist's record. 



Lynns of Wales or the Meres of Cumberland '? Why has such a species 

 as Cyinindia vaporariornm never been taken on any of the Surrey 

 heaths, whereas, at no higher elevation or differently conditioned 

 locality, it occurs at Heswall in Cheshire '? The assumption that these 

 species did once occur all along the line of their march, under suitable 

 conditions, but have been exterminated by younger and more vigorous 

 immigrants, will not I think stand, for extermination implies competi- 

 tion, and competition a similarity of habitat and economy, and between 

 these species and those which have by this supposition supplanted 

 them, the dissimilarity of habitat and economy is absolute. Such a 

 species as Carabus dathratus is not a beetle easily overlooked, and 

 would probably have been discovered if it existed in Wales where areas 

 apparently eminently suitable for it are abundant, and I might 

 considerably multiply such examples. The force of such evidence to 

 me appears to be that the members of this north-western group never 

 did cross the lowland plain of eastern England at all, and that conse- 

 quently the area of their origin must be looked for elsewhere than in 

 continental Europe. 



There are, indeed, in other groups of our fauna and flora, indications 

 which point to another possible solution of this problem. A few years 

 ago three species of north American freshwater sponges were discovered 

 in the w^est of Ireland — species not yet found elsewhere in Europe. The 

 presence of these can only be explained by the supposition of a former 

 land connexion which closed in the Atlantic on the north, and united 

 Ireland and Scotland with Greenland and North America by way of the 

 Faroe Islands and Iceland to the north and Norway to the north-east. 

 Such an area, if it existed in late tertiary times, might well have been 

 peopled by a fauna which we discover now in its remaining fragments. 

 We must also renounce the idea of a vast ice or snow-sheet covering 

 the whole of Great Britain during the Glacial period, w'e must imagine 

 these species which we are considering dri\en south by the advent of 

 the cold epoch instead of led up north-westerly at its conclusion, and 

 resident in these islands, but probably with a range much more 

 southerly than at present, during all those ages of lowered temperature 

 when no doubt there were glaciers over all the mountain districts of 

 Ireland, Scotland, the north of England and ^^'ales. As the mean 

 temperature gradually rose century after century such species as had 

 advanced furthest south shrank back, not through stress of any compe- 

 tition, but through a physiological necessity of association with certain 

 climatic and other conditions. 



Thus we may explain the presence of two or three species of 

 lli/drnpm i, iindoubtedly members of this group, in Surrey, and of others 

 in Devonshire, as the vestiges of a range much further south than at 

 present, and which has been maintained in these isolated detachments 

 through the environment having continued to a great extent 

 unchanged, that environment being aquatic, and subject to some- 

 what other than terrestrial conditions. 



No doubt before the conclusion of the Glacial epoch great changes 

 in the distribution of sea and land had taken place. This country 

 may have been reduced to the condition of a more or less connected 

 archipelago, but I doubt if there is any evidence whatever from the 

 biological side to support the hypothesis of a total submergence. 

 Certainly before the complete passing away of Glacial conditions, the 

 suppositious connection between Ireland, Scotland, and Norway must 



