The Wallace-Darwin Correspondence 



lem, which I believe beats the plate on the circular riin; 

 but I will sometime. I foresee, however, that there are so 

 many doubtful points that we shall never agree. As far 

 as a glance serves it seems to me, perhaps falsely, that 

 you sometimes argue that hybrids have an advantage from 

 greater vigour, and sometimes a disadvantage from not 

 being so well fitted to their conditions. Heaven protect 

 my stomach whenever I attempt following your argument ! 

 —Yours most sincerely, C. Darwin. 



Down, Bromley, Kent. April 6, 1868. 



My dear Wallace, — I have been considering the terrible 

 problem. Let me first say that no man could have more 

 earnestly wished for the success of Natural Selection in 

 regard to sterility than I did, and when I considered a 

 general statement (as in your last note) I always felt sure 

 it could be worked out, but always failed in detail, the 

 cause being, as I believe, that Natural Selection cannot 

 effect what is not good for the individual, including in 

 this term a social community. It would take a volume to 

 discuss all the points; and nothing is so humiliating to 

 me as to agree with a man like you (or Hooker) on the 

 premises and disagree about the result. 



I agree with my son's argument and not with rejoinder. 

 The cause of our difference, I think, is that I look at the 

 number of offspring as an important element (all circum- 

 stances remaining the same) in keeping up the average 

 number of individuals within any area. I do not believe 

 that the amount of food by any means is the sole deter- 

 mining cause of number. Lessened fertility is equivalent 

 to a new source of destruction. I believe if in one district 

 a species produce from any cause fewer young, the defi- 

 ciency would be supplied from surrounding districts. This 

 applies to your par. 5. If the species produced fewer young 



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