CHAP. XVI THE BRITISH ISLES 371 



British Isles with the adjacent continent is not altogether 

 correct. Among birds we have undoubted peculiarities in 

 at least three instances ; peculiar fishes are much more 

 numerous, and in this case the fact that the Irish species 

 are almost all different from the British, and those of the 

 Orkneys distinct from those of Scotland, renders it almost 

 certain that the great majority of the fourteen peculiar 

 British fishes are really peculiar and wall never be found 

 on the European continent. The mosses and Hepaticse 

 also have been sufficiently collected in Europe to render 

 it pretty certain that the more remarkable of the peculiar 

 British forms are not found there ; why therefore, it may 

 be well asked, should there not be a proportionate number 

 of peculiar British insects ? It is true that numerous 

 species have been first discovered in Britain, and, sub- 

 sequently, on the continent ; but we have many species 

 which have been known for twenty, thirty, or forty years, 

 some of which are not rare with us, and yet have never 

 been found on the continent. We have also the curious 

 fact of our outlying islands, such as the Shetland Isles, 

 the Isle of Man, and the little Lundy Island, possessing 

 each some peculiar forms which, certainly, do not exist 

 on our principal island w^hich has been so very thoroughly 

 worked. Analogy, therefore, w^ould lead us to conclude 

 that many other species or varieties may exist on our 

 islands and not on the continent ; and when we find that 

 a very large number (150) in three orders only, are so 

 recorded, we may, I think, be sure that some considerable 

 portion of these (though how many we cannot say) are 

 really endemic British species. 



The general laws of distribution also lead us to expect 

 such phenomena. Very rare and very local species are 

 such as are becoming extinct , and it is among insects, which 

 are so excessively varied and abundant, which present so 

 many isolated forms, and which, even on continents, afford 

 numerous examples of very rare species confined to re- 

 stricted areas, that we should have the best chance of 

 meeting with every degree of rarity down to the point of 

 almost complete extinction. But we know that in all 

 parts of the world islands are the refuge of species or 



