374 MY LIF E 



however much patience I had worked and experimented on 

 the subject, I could never have approached the completeness 

 of his book, its vast accumulation of evidence, its overwhelm- 

 ing argument, and its admirable tone and spirit. I really feel 

 thankful that it has not been left to me to give the theory to 

 the world. Mr. Darwin has created a new science and a new 

 philosophy; and I believe that never has such a complete 

 illustration of a new branch of human knowledge been due 

 to the labours and researches of a single man. Never have 

 such vast masses of widely scattered and hitherto quite uncon- 

 nected facts been combined into a system and brought to 

 bear upon the establishment of such a grand and new and 

 simple philosophy. 



" I am surprised at your joining the north and south banks 

 of the lower Amazon into one region. Did you not find a 

 sufficiency of distinct species at Obydos and Barra to separate 

 them from Villa Nova and Santarem? I am now convinced 

 that insects, on the whole, do not give such true indications 

 of zoological geography as birds and mammals, because, first, 

 they have such immensely greater means of dispersal across 

 rivers and seas ; second, because they are so much more 

 influenced by surrounding circumstances ; and third, because 

 the species seem to change more quickly, and therefore dis- 

 guise a comparatively recent identity. Thus the insects of 

 adjacent regions, though originally distinct, may become 

 rapidly amalgamated, or portions of the same region may 

 come to be inhabited by very distinct insect-faunas owing to 

 differences of soil, climate, etc. This is strikingly shown 

 here, where the insect-fauna from Malacca to New Guinea 

 has a very large amount of characteristic uniformity, while 

 Australia, from its distinct climate and vegetation, shows a 

 wide difference. I am inclined to think, therefore, that a pre- 

 liminary study of, first, the mammals, and then the birds, 

 is indispensable to a correct understanding of the geographi- 

 cal and physical changes on which the present insect-distribu- 

 tion depends. 1 



1 These ideas were thoroughly worked out in my book on " The 

 Geographical Distribution of Animals," published in 1876. 



