646 MR. H. J. ELWES ON THE GEOGRAPHICAL [June 17, 



The attempt to account for the various facts which are here and 

 there brought to light is a task far beyond my power or inclination, 

 more especially as I do not see how we can speculate with much 

 advantage on the causes which have influenced the distribution of 

 birds whilst our ignorance of the distribution of other animals is so 

 great. 



On the map (Plate LI.) to which I beg leave to draw your atten- 

 tion, I have shown the ornithological divisions into which I believe 

 Asia may be divided ; and though, as is obvious, a hard and fast line 

 can never be drawn between the different regions and subregions, yet 

 in some places (as, for instance, "Wallace's line" and the Himalaya 

 mountains) they are separated by a distance which is on the map 

 hardly appreciable. 



'Ihe connexion between climate, physical geography, and ornitho- 

 logy is much closer in Asia than would be supposed by any one who 

 had not travelled there. All over the Indo-Malay region, wherever 

 hills exceeding 3000 or 4000 feet high are found, a moister climate 

 and more luxuriant vegetation is sure to be accompanied by a corre- 

 sponding change in the birds. 



So much is this the case that wherever in India, South China, and 

 the Indo-Chinese countries an elevation of 4000 feet is reached, some 

 of the birds characteristic of the Himalaya are almost sure to be found. 



Another point that has struck me is that in Asia almost every 

 genus of birds found in Europe is represented by some, and often by a 

 greater number of similar or allied species. This would seem to 

 show, what I believe is equally true of plants and animals, that the 

 birds of Europe have been derived from the east ; and though we 

 have got into a habit of considering many genera of birds especially 

 characteristic of Europe, it is only because we know so much less of 

 their distribution in Asia. 



This of course applies principally to the temperate regions of 

 Northern and Central Asia; but I think it impossible to gain a 

 correct idea of European ornithology without a considerable know- 

 ledge of the whole Paleearctic avifauna. 



A large number of genera and families found in Tropical Asia are 

 also common to Africa ; and though I do not think we can place the 

 two continents in the same zoological region (as Mr. Murray has done 

 in his work, ' The Geographical Distribution of Mammalia '), yet 

 I believe a careful comparison of generic forms from Africa and Asia 

 would result in the union of several genera which are now separated. 



One of my greatest difficulties has been the want of a really reli- 

 able work on the genera of birds ; for though I have in most cases 

 followed the arrangement of Mr. Gray's ' Hand-list,' I have often 

 found that the uncertainty of classification which prevails has dimi- 

 nished the confidence which I should otherwise have had in some 

 portions of my work. 



I will now endeavour to show how far the conclusions I have 

 formed are borne out by facts, and hope that my attempt to deal in 

 a connected manner with so vast a subject will be found to contain 

 the elements of truth. 



