GEOGRAPHICAL DISTRIBUTION [CHAP. VII 



stter 395 ^^ perhaps there was during long ages a small isolated 

 continent in the S. Hemisphere which served as the birth- 

 place of the higher plants but this is a wretchedly poor 

 conjecture. It is odd that Ball does not allude to the obvious 

 fact that there must have been alpine plants before the 

 Glacial period, many of which would have returned to the 

 mountains after the Glacial period, when the climate again 

 became warm. I always accounted to myself in this manner 

 for the gentians, etc. 



Ball ought also to have considered the alpine insects 

 common to the Arctic regions. I do not know how it may 

 be with you, but my faith in the glacial migration is not at all 

 shaken. 



Letter 396 A. R. Wallace to C. Darwin. 



This letter is in reply to Mr. Darwin's criticisms on Mr. Wallace's 

 Island Life, 1880. 



Pen-y-Bryn, St. Peter's Road, Croydon, Nov. 8th, 1880. 



Many thanks for your kind remarks and notes on my book. 

 Several of the latter will be of use to me if I have to prepare a 

 second edition, which I am not so sure of as you seem to be. 



1. In your remark as to the doubtfulness of paucity of 

 fossils being due to coldness of water, I think you overlook 

 that I am speaking only of water in the latitude of the Alps, 

 in Miocene and Eocene times, when icebergs and glaciers 

 temporarily descended into an otherwise warm sea ; my 

 theory being that there was no Glacial epoch at that time, but 

 merely a local and temporary descent of the snow-line and 

 glaciers owing to high excentricity and winter in aphelion. 



2. I cannot see the difficulty about the cessation of the 

 Glacial period. 



Between the Miocene and the Pleistocene periods geo- 

 graphical changes occurred which rendered a true Glacial 

 period possible with high excentricity. When the high 

 excentricity passed away the Glacial epoch also passed away 

 in the temperate zone ; but it persists in the arctic zone, 

 where, during the Miocene, there were mild climates, and this 

 is due to the persistence of the changed geographical con- 

 ditions. The present arctic climate is itself a comparatively 

 new and abnormal state of things, due to geographical 

 modification. 



