14 GEOGRAPHICAL DISTRIBUTION [Chap. VII 



Letter 390 further on. I am positively against any Southern continent 

 as uniting South America with Australia or New Zealand, 

 as you will see at Vol. I., pp. 398-403, and 459-66. My 

 general conclusions as to distribution of land mollusca 1 are 

 at Vol. II., pp. 522-9. When you have read these passages, 

 and looked at the general facts which lead to them, I shall 

 be glad to hear if you still differ from me. 



Though, of course, present results as to the origin and 

 migrations of genera of mammals will have to be modified 

 owing to new discoveries, I cannot help thinking that much 

 will remain unaffected, because in all geographical and 

 geological discoveries the great outlines are soon reached, 

 the details alone remain to be modified. I also think much 

 of the geological evidence is now so accordant with, and 

 explanatory of, Geographical Distribution, that it is prima 

 facie correct in outline. Nevertheless, such vast masses of 

 new facts will come out in the next few years that I quite 

 dread the labour of incorporating them in a new edition. 



I hope your health is improved ; and when, quite at your 

 leisure, you have waded through my book, I trust you will 

 again let me have a few lines of friendly criticism and advice. 



Letter 391 To A. R. Wallace. 



Down, June 17th, 1876. 

 I have now finished the whole of Vol. I., with the same 

 interest and admiration as before ; and I am convinced that 

 my judgment was right and that it is a memorable book, 

 the basis of all future work on the subject. I have nothing 

 particular to say, but perhaps you would like to hear my 

 impressions on two or three points. Nothing has struck 

 me more than the admirable and convincing manner in 

 which you treat Java. To allude to a very trifling point, 

 it is capital about the unadorned head of the Argus-pheasant. 2 



1 Geogr. Distrib., II., pp. 524, 525. Mr. Wallace points out that 

 "hardly a small island on the globe but has some land- shells peculiar to 

 it " — and he goes so far as to say that probably air-breathing mollusca 

 have been chiefly distributed by air- or water-carriage, rather than by 

 voluntary dispersal on the land. 



2 See Descent of Man, Ed. 1., pp. 90 and 143, for drawings of the 

 Argus pheasant and its markings. The ocelli on the wing feathers were 

 favourite objects of Mr. Darwin, and sometimes formed the subject of the 



