CHAr. XVI.] 



THE BRITISH ISLEa 



345 



poAver, as we shall find Avlien we come to treat of the floras of 

 oceanic islands ; and we believe that the explanation of this is, 

 that the life of species, and especially of genera, is often so 

 prolonged as to extend over whole cycles of such terrestrial 

 mutations as we have just referred to ; and that thus the 

 majority of plants are afforded means of dispersal which are 

 usually sufficient to carry them into all suitable localities on the 

 globe. Hence it follows that their actual existence in such 

 localities depends mainly upon vigour of constitution and adap- 

 tation to conditions just as it does in the case of the lower and 

 more rapidly diffused groups, and only partially on superior 

 facilities for diffusion. This important principle will be used 

 further on to afford a solution of some of the most difficult 

 problems in the distribution of plant life. 



Concluding remarks on the Feculiarities of the British Fauna and 

 Flora. — The facts, now I believe for the first time, brought to- 

 gether respecting the peculiarities of the British fauna and flora, 

 are sufficient to show that there is considerable scope for the study 

 of geographical distribution even in so apparently unpromising 

 a field as one of the most recent of continental islands. Looking 

 at the general bearing of these facts, they prove, that the idea 

 so generally entertained as to the biological identity of the 

 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 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 fifteen peculiar British fishes are really peculiar and will never 

 be found on the European Continent. The mosses and Hepaticae 

 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 dis- 

 covered in Britain, and, subsequently, 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 



