Ixvii 



of Madagascar, may Avell be due to a concurrence of events as rare 

 and improbable as this seems to be. 



The Azores, and in a less degree the Madeiras, appear to me 

 to teach us this important lesson in the laws of distribution of 

 birds and insects, — that it has been determined neither by the 

 direction of ocean currents nor by that of the most prevalent 

 winds, but almost wholly by such more exceptional causes as 

 storms and hurricanes, which still continue to bring immigrants 

 from the nearest lands. 



Mr. Murray's argument for a land-connection between the 

 various Atlantic islands, from the Azores to the Cape de Verdes, 

 and even to St. Helena, has perhaps more to be said for it ; but 

 I do not think that the facts require anything beyond the exten- 

 sion of each group into a considerable mass of land. Such an 

 extension is indicated by the comparatively elevated submarine 

 bank on which each group stands ; and it is evident that more 

 extended land-surfaces would not only bring the groups nearer to 

 each other, but, by offering a much greater length of opposing 

 coasts, would greatl}'^ facilitate the migration and accidental 

 transmission of individuals. 



The most bold and original, and perhaps the most useful, 

 generalization in Mr. Murray's paper, is his classification of all 

 Coleoptera into three grand stirpes or geographical races — the 

 Indo-African, the Brazilian, and the Microtypal. The difficult}^ 

 of forming any such broad divisions in so vast and complicated a 

 group is very great, and has never hitherto been attempted ; and 

 though it is hardly likely that a true classification should have 

 been hit upon at once, the present one will, I believe, prove very 

 useful as a provisional hypothesis which every student will be 

 able to test in his own special branch of study. Almost every one 

 will admit that the Brazilian or South American division is a 

 natural one ; and the Indo-African will also probabl}' be accepted ; 

 and these comprise the whole of the intertropical faunas. But 

 the Microtypal, comprising the temperate faunas of the whole 

 world in one group of equal value to each of the others, will be 

 as generally rejected. It is, however, undoubtedly the fact that 

 certain similarities do run through all the temperate faunas, and 

 Mr. Murray has done good service by so energetically calling 

 attention to this fact. The question to be decided is, whether 

 this similarity is fundamental or superficial. Is it the record of 



