18641869] PANGENESIS 3<DI 



compounded of numbers of Spencer's physiological units) is the Letter 218 

 only difficulty ; but that is only on a par with the difficulties 

 in all conceptions of matter, space, motion, force, etc. 



As I understood Spencer, his physiological units were 

 identical throughout each species, but slightly different in 

 each different species ; but no attempt was made to show how 

 the identical form of the parent or ancestors came to be 

 built up of such units. 



To A. R. Wallace. Letter 219 



Down, Feb. 2yth [1868]. 



You cannot well imagine how much I have been pleased 

 by what you say about pangenesis. None of my friends will 

 speak out, except to a certain extent Sir H. Holland, who 

 found it very tough reading, but admits that some view 

 " closely akin to it " will have to be admitted. Hooker, as far 

 as I understand him, which I hardly do at present, seems to 

 think that the hypothesis is little more than saying that 

 organisms have such and such potentialities. What you say 

 exactly and fully expresses my feelings viz., that it is a relief 

 to have some feasible explanation of the various facts, which 

 can be given up as soon as any better hypothesis is found. 

 It has certainly been an immense relief to my mind ; for I 

 have been stumbling over the subject for years, dimly seeing 

 that some relation existed between the various classes of 

 facts. I now hear from H. Spencer that his views quoted in 

 my footnote refer to something quite distinct, as you seem to 

 have perceived. 1 



A. R. Wallace to C. Darwin. Letter 220 



Hurstpierpoint, March ist, 1868. 



. . . Sir C. Lyell spoke to me as if he has greatly admired 

 pangenesis. I am very glad H. Spencer at once acknow- 

 ledges that his view was something quite distinct from yours. 

 Although, as you know, I am a great admirer of his, I feel 

 how completely his view failed to go to the root of the matter, 

 as yours does. His explained nothing, though he was 

 evidently struggling hard to find an explanation. Yours, as far 

 as I can see, explains everything in growth and reproduction- 



1 This letter is published in Life and Letter s, III., p. 79. 



