38 



islands present parallel modifications, where that line 

 is to be drawn. Meanwhile, how far geographical va- 

 rieties of this kind, concerning the non-specific claims 

 of which confessedly but little doubt can exist, may lead 

 to the explanation of the Transatlantic ones just referred 

 to, I will not venture to suggest. Yet certain it is, that 

 the one case bears directly on the other ; and that, if 

 we can prove that common European insects, when iso- 

 lated in the ocean, become in nearly all cases more or 

 less modified externally in form, there is at least pre- 

 sumptive evidence that the law will hold good on a 

 wider scale, and may be extended, not only to the 

 Atlantic itself, but even to countries beyond. The dif- 

 ferences of the present Dromius from its more northern 

 representatives are, as just stated, small; nevertheless, 

 since they are fixed, those naturalists who do not believe 

 in geographical influence might choose to consider them 

 of sufficient importance to erect a new species upon. 

 But after a careful comparison of this with other insects 

 similarly circumstanced, I am convinced that the modi- 

 fications in question are merely local ones, and such 

 as may be reasonably accounted for by the combined 

 agencies of latitude and isolation, and the consequently 

 altered habits of the creature, which is thus compelled 

 to seek alpine localities in lieu of its natural ones*." 



In like manner the Calathus fuscus, Fab., the Ancho- 

 menus marginatus, Linn., and the Anthicus fenestratus, 

 Schmidt, which occur almost exclusively in the lower 

 * Insecta Maderensia (London, 1854), pp. 7, 8, 9. 



