Alfred Russel Wallace 



{Second and third sheets of a letter from Wallace, apparently of 

 February, 1868.) 



I am in the second volume of your book, and I have 

 been astonished at the immense number of interesting facts 

 you have brought together. I read the chapter on Pan- 

 genesis first, for I could not wait. I can hardly tell you 

 how much I admire it. It is a positive comfort to me to 

 have any feasible explanation of a difficulty that has always 

 been haunting me, and I shall never be able to give it up 

 till a better one supplies its place, and that I think hardly 

 possible. You have now fairly beaten Spencer on his own 

 ground, for he really offered no solution of the difficulties 

 of the problem. The incomprehensible minuteness and vast 

 numbers of the physiological germs or atoms (which them- 

 selves must be compounded of numbers of Spencer's physio- 

 logical units) is the 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 physio- 

 logical 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. 



The only parts I have yet met with where I somewhat 

 differ from your views are in the chapter on the Causes 

 of Variability, in which I think several of your argu- 

 ments are unsound : but this is too long a subject to go 

 into now. 



Also, I do not see your objection to sterility between 

 allied species having been aided by Natural Selection. It 

 appears to me that, given a differentiation of a species into 

 two forms, each of which was adapted to a special sphere 

 of existence, every slight degree of sterility would be a 

 positive advantage, not to the individuals who were sterile, 



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