'SO EVOLUTION [Chap. Ill 



Letter ioo on the subject to him, you would ask him whether it was 

 not allowable (and a great step) to invent the undulatory 

 theory of light, i.e. hypothetical undulations, in a hypothetical 

 substance, the ether. And if this be so, why may 1 not 

 invent the hypothesis of Natural Selection (which from the 

 analogy of domestic productions, and from what we know 

 of the struggle for existence and of the variability of organic 

 beings, is, in some very slight degree, in itself probable) and 

 try whether this hypothesis of Natural Selection does not 

 explain (as I think it does) a large number of facts in 

 geographical distribution— geological succession, classification, 

 morphology, embryology, etc. I should really much like to 

 know why such an hypothesis as the undulation of the ether 

 may be invented, and why I may not invent (not that I did 

 invent it, for I was led to it by studying domestic varieties) 

 any hypothesis, such as Natural Selection. 



Pray forgive me and my pen for running away with me, 

 and scribbling on at such length. 



I can perfectly understand Sedgwick l or any one saying 

 that Natural Selection does not explain large classes of facts ; 

 but that is very different from saying that I depart from 

 right principles of scientific investigation. 



Letter 101 To J. S. Henslow. 



Down, May 14th [rS6o]. 

 I have been greatly interested by your letter to Hooker, 

 and I must thank you from my heart for so generously 

 defending me, as far as you could, against my powerful 

 attackers. Nothing which persons say hurts me for long, for 

 I have an entire conviction that I have not been influenced 

 by bad feelings in the conclusions at which I have arrived. 

 Nor have I published my conclusions without long delibera- 

 tion, and they were arrived at after far more study than the 

 public will ever know of, or believe in. I am certain to have 

 erred in many points, but I do not believe so much as 

 Sedgwick and Co. think. 



Is there any Abstract or Proceedings of the Cambridge 



1 See Life and Letters, II., p. 247; the letter is there dated 

 December 24th, but must, we think, have been written in November at 

 latest. 



