18431882] GLACIAL PERIOD 465 



regions ; but I can make no answer to your argument, and Letter 353 

 am completely in a cleft stick. By an odd chance I have 

 only a few days ago been discussing this subject, in relation 

 to plants, with Dr. Hooker, who believes to a certain extent, 

 but strongly urged the little apparent extinction in the 

 equatorial regions. I stated in a letter some days ago to him 

 that the tropics of S. America seem to have suffered less 

 than the Old World. There are many perplexing points ; 

 temperate plants seem to have migrated far more than 

 animals. Possibly species may have been formed more 

 rapidly within tropics than one would have expected. I 

 freely confess that you have confounded me ; but I cannot 

 yet give up my belief that the Glacial period did to certain 

 extent affect the tropics. 



To J. D. Hooker. Letter 354 



Down, Feb. 25th [1862]. 



I have almost finished your Arctic paper, 1 and I must tell 

 you how I admire it. The subject, treated as you have 

 treated it, is really magnificent. Good Heaven, what labour 

 it must have cost you ! And what a grand prospect there is 

 for the future. I need not say how much pleased I am at 

 your notice of my work ; for you know that I regard your 

 opinion more than that of all others. Such papers are the real 

 engine to compel people to reflect on modification of species ; 

 any one with an enquiring mind could hardly fail to wish to 

 consider the whole subject after reading your paper. By 

 Jove ! you will be driven, nolens volens, to a cooled globe. 

 Think of your own case of Abyssinia and Fernando Po, 

 and South Africa, and of your Lebanon case 2 ; grant that 

 there are highlands to favour migration, but surely the low- 

 lands must have been somewhat cooled. What a splendid 

 new and original evidence and case is that of Greenland : I 

 cannot see how, even by granting bridges of continuous land, 

 one can understand the existing flora. I should think from 

 the state of Scotland and America, and from isothermals, 



1 "Outlines of the Distribution of Arctic Plants" [Read June 2ist, 

 1860], Linn. Soc. Trans., XXIII., 1862, p. 251. The author's remarks on 

 Mr. Darwin's theories of Geographical Distribution are given at p. 255 : 

 they are written in a characteristically generous spirit. 



2 See Origin^ Ed. vi., p. 337. 



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