1867—1882] Wallace's book 13 



doubt that you will succeed, owing to your new argument! 389 



and the coloured chart. Of a special value, as it seems to 

 me, is the conclusion that we must determine the an 

 chiefly by the nature of the mammals. When I worked 

 many years ago on this subject, I doubted much whether 

 the now-called Palaearctic and Nearctic regions ought to be 

 separated ; and I determined if 1 made another region that 

 it should be Madagascar. I have, therefore, been able to 

 appreciate your evidence on these points. What progress 

 Palaeontology has made during the last twenty years ! but 

 if it advances at the same rate in the future, our views on 

 the migration and birthplace of the various groups will, I 

 fear, be greatly altered. I cannot feel quite easy about the 

 Glacial period, and the extinction of large mammals, but I 

 must hope that you are right. I think you will have to 

 modify your belief about the difficulty of dispersal of land 

 molluscs ; I was interrupted when beginning to experimentise 

 on the: just hatched young adhering to the feet of ground- 

 roosting birds. I differ on one other point — viz. in the belief 

 that there must have existed a Tertiary Antarctic continent, 

 from which various forms radiated to the southern extremities 

 of our present continents. But I could go on scribbling for 

 ever. You have written, as 1 believe, a grand and memorable 

 work, which will last for years as the foundation for all future 

 treatises on Geographical Distribution. 



P.S. — You have paid me the highest conceivable com- 

 pliment, by what you say of your work in relation to my 

 chapters on distribution in the Origin, and I heartily thank 

 you for it. 



From A. R. Wallace to C. Darwin. Letter 390 



The Dell, Grays, Essex, June 7th. 1S76. 

 Many thanks for your very kind letter. So f« w people 

 will read my book at all regularly, that a criticism from one 

 who does so will be very welcome. If, as I sup] ose, it 

 only to p. 1S4 of Vol. I. that you have read, you cannot 

 yet quite see my conclusions on the points you refer to inland 

 molluscs and Antarctic continent). My own conclusion 

 fluctuated during the progress of the book, and 1 hive, I 

 know, occasionally used expressions (the relics of earlier 

 ideas) which are not quite consistent with what I say 



