1843—1882] GLACIAL PERIOD 4<J3 



I demur to what you say that we change climate of the Letter 344 

 world to account for "migration of bugs, flies, etc." We 

 do nothing of the sort ; for we rest on scored rocks, old 

 moraines, arctic shells, and mammifers. I have no theory 

 whatever about cause of cold, no more than I have for 

 cause of elevation and subsidence ; and I can see no reason 

 why I should not use cold, or elevation, or subsidence to 

 explain any other phenomena, such as distribution. 1 think 

 if I had space and time I could make a pretty good case 

 against any great continental changes since the Glacial 

 epoch, and this has mainly led me to give up the Lyellian 

 doctrine as insufficient to explain all mutations of climate. 



I was amused at the British Museum evidence. 1 I am 

 made to give my opinion so authoritatively on botanical 

 matters ! . . . 



As for our belief in the origin of species making any 

 difference in descriptive work, I am sure it is incorrect, for 

 I did all my barnacle work under this point of view. Only 

 I often groaned that I was not allowed simply to decide 

 whether a difference was sufficient to deserve a name. 



I am glad to hear about Iluxlcy — a wonderful man. 



To J. D. Hooker. Letter 345 



Wells Terrace, Ilkley, Otley, Yorkshire, 



Thursday [before Dec. 9th, 1859]. 



I have read your discussion, 2 as usual, with great interest. 

 The points are awfully intricate, almost at present beyond the 

 confines of knowledge. The view which I should have looked 

 at as perhaps most probable (though it hardly differs from 

 yours) is that the whole world during the Secondary ages was 

 inhabited by marsupials, araucarias (Mem. — Fossil wood so 

 common of this nature in South America 3 ), Banksia, etc.; 

 and that these were supplanted and exterminated in the 

 greater area of the north, but were left alive in the south. 



1 This refers to the letter to Murchison (Letter 65, pp. 109-10), 

 published with the evidence of the 1858 enquiry by the Trustees of the 

 British Museum. 



2 See Introductory Essay, p. c. Darwin did not receive this work 

 until Dec. 23rd, so that the reference is to proof-sheets. 



3 See Letter 6, Note 1, p. 23. 



