1858.] CLIMATE AND MIGRATION. 4^3 



with new forms would be very liable to be improved or modi- 

 fied by natural selection, to adapt them to the new forms 

 with which they had to compete ; hence most of the forms 

 on the mountains of the Tropics are not identical, but ;'^- 

 rese?itattve forms of North temperate plants. 



There are similar classes of facts in marine productions. 

 All this will appear very rash to you, and rash it may be ; 

 but I am sure not so rash as it will at first appear to you : 

 Hooker could not stomach it at all at first, but has become 

 largely a convert. From mammalia and shallow sea, I believe 

 Japan to have been joined to main land of China within no 

 remote period ; and then the migration north and south be- 

 fore, during, and after the Glacial epoch would act on Japan, 

 as on the corresponding latitude of China and the United 

 States, 



I should beyond anything like to know whether you have 

 any Alpine collections from Japan, and what is their charac- 

 ter. This letter is miserably expressed, but perhaps it will 

 suffice to show what I believe have been the later main mi- 

 grations and changes of temperature. . . . 



C. Darwin to J. D. Hooker. 



[Down] Oct. 6th, 1858. 



... If you have or can make leisure, I should very much 

 like to hear news of Mrs. Hooker, yourself, and the children. 

 Where did you go, and what did you do and are doing? 

 There is a comprehensive text. 



You cannot tell how I enjoyed your little visit here. It 

 did me much good. If Harvey is still with you, pray remem- 

 ber me very kindly to him. 



... I am working most steadily at my Abstract, but it 

 grows to an inordinate length ; yet fully to make my view 

 clear (and never giving briefly more than a fact or two, and 

 slurring over difficulties), I cannot make it shorter. It will 

 yet take me three or four months ; so slow do I work, though 

 never idle. You cannot imagine what a service you have 



