Correspondence on Biology, etc. 



according to the law of averages ? Will it not be about 

 1 in 64 ? If so it is ample — in many cases — for Natural 

 Selection to work on, because in many cases less than ^ 

 of offspring survives. 



On Romanes' view of the impossibility of Natural Selec- 

 tion doing anything alone, because the required coincident 

 variations do not occur, the occurrence of a '* strong man " 

 or a racehorse that beats all others easily must be impos- 

 sible, since in each of these cases there must be scores of 

 coincident favourable variations. 



Given sufficient variation, I believe divergent modifi- 

 cation of a species in two lines could easily occur, even if 

 free intercrossing occurred, because, the numbers varying 

 being a large proportion of the whole, the numbers which 

 bred like with like would be sufficient to carry on the two 

 lines of divergence, those that intercrossed and produced 

 less perfectly adapted offspring being eliminated. Of course 

 some amount of segregate breeding does always occur, as 

 Darwin always maintained, but, as he also maintained, it 

 is not absolutely essential to evolution. Romanes argues 

 as if "free intercrossing" meant that none would pair 

 like with like ! I hope you will have another slap at him, 

 and withdraw or explain that unlucky '' infinity to one/' 

 which is Romanes' sheet-anchor. — Yours very truly, 



Alfred R. Wallace. 



To Prop. Poulton 



Parkstone, Dorset. June 16, 1892. 



My dear Mr. Poulton, — Many thanks for sending me 

 Weismann's additional Essays,^ which I look forward to 

 reading with much pleasure. I have, however, read the 

 first, and am much disappointed with it. It seems to me 



* " Essays upon Heredity and Kindred Biological Problems," VoL IL 1892. 



51 



