DEPRIVATION OF BEITISH COLEOPTEBA. 181 



Indeed, none of these various schemes, conjectures, and 

 hypotheses will stand working out in complete detail. All 

 we can hope to do, at any rate at present, is to get hold 

 of some few general principals, and to test those by all the 

 evidence at our command, and by application to the whole 

 of both fauna and flora. 



Some such principles I hope emerge from the fog of 

 conjecture through which we have been travelling. As 

 that we can certainly detect a threefold, if not a fourfold, 

 disparity in our insect fauna ; that its phenomena point, 

 at any rate, to past land extensions to the north-west 

 and to the south-west, now entirely swept away; that 

 Ireland must have been separated from the greater part 

 of England by an obstacle of some kind while the fauna 

 was in process of establishment, and while or after it was 

 itself continuous with an extension of Western Europe, 

 and that it is not impossible that some extreme estimate 

 of the severity of the glacial climate may require modifi- 

 tion. Furthermore, that if any of our Coleoptera can be 

 termed autochthonous, the northern or Celtic element is 

 the only one that can be so regarded, and that, while all 

 the rest of the fauna seems to have been derived from the 

 south and east, this only may have had a northern origin 

 and be possibly pre-glacial. These are conclusions which 

 we may perhaps entertain as provisional hypothesis. For 

 the rest, perhaps all I have succeeded in making plain is 

 how vastly our ignorance exceeds our knowledge of the 

 factors of the problem ; and this is especially the case 

 with a group of insects such as we have been considering. 

 For mark the difficulties of the quest. Insects, although, 

 because they are probably much older as distinct species, 

 and also because both specifically and individually they 

 are very much more numerous than the higher vertebrata, 

 furnish more abundant evidence of faunistic distribution, 



