18641869] STERILITY OF HYBRIDS 299 



gross misstatements of the Athen&um ; and also says a Letter 216 

 word in favour of pangenesis. I think we may now con- 

 gratulate you on having made a valuable convert, whose 

 opinions on the subject, coming so late and being evidently 

 so well considered, will have much weight. 



I am going to Norwich on Tuesday to hear Dr. Hooker, 

 who I hope will boldly promulgate " Darwinism ' in his 

 address. 1 Shall we have the pleasure of seeing you there? 



I am engaged in negociations about my book. 



Hoping you are well and getting on with your next 

 volumes. 



We are permitted by Mr. Wallace to append the following note 

 as to his more recent views on the question of Natural Selection and 

 sterility : 



" When writing my Darwinism, and coming again to the considera- 

 tion of this problem of the effect of Natural Selection in accumulating 

 variations in the amount of sterility between varieties or incipient 

 species twenty years later, I became more convinced, than I was 

 when discussing with Darwin, of the substantial accuracy of my argu- 

 ment. Recently a correspondent who is both a naturalist and a 

 mathematician has pointed out to me a slight error in my calcula- 

 tion at p. 183 (which does not, however, materially affect the result), 

 disproving the ' physiological selection ' of the late Dr. Romanes, but 

 he can see no fallacy in my argument as to the power of Natural 

 Selection to increase sterility between incipient species, nor, so far as 

 I am aware, has any one shown such fallacy to exist. 



" On the other points on which I differed from Mr. Darwin in 

 the foregoing discussion the effect of high fertility on population of 

 a species, etc. I still hold the views I then expressed, but it would 

 be out of place to attempt to justify them here." 



A. R. W. (1899). 



To C. Lyell. Letter 217 



Down, Oct. 4th [1867]. 



With respect to the points in your note, I may sometimes 

 have expressed myself with ambiguity. At the end of 

 Chapter XXII I., where I say that marked races are not 

 often (you omit " often ") produced by changed conditions, 2 



1 Sir Joseph Hooker's Presidential Address at the British Associa- 

 tion Meeting. 



" Hence, although it must be admitted that new conditions of life 

 do sometimes definitely affect organic beings, it may be doubted whether 

 well-marked races have often been produced by the direct action of 

 changed conditions without the aid of selection either by man or nature." 

 {Animals and Plants, Vol. II., p. 292, 1868.) 



