Alfred Russel Wallace 



about by Natural Selection, just as extreme fecundity had 

 been brought about (by Natural Selection) in cases where 

 such fecundity was of advantage. 



To Prof. Meldola 



Frith Hill, Godalming. April 12, 1888. 



My dear Meldola, — Many thanks for your criticism. It 

 is a perfectly sound one as against my view being a com- 

 plete explanation of the phenomena, but that I do not 

 claim. And I do not see any chance of the required facts 

 being forthcoming for many years to come. Experiments 

 in the hybridisation of animals are so difficult and tedious 

 that even Darwin never undertook any, and the only people 

 who could and ought to have done it — the Zoological Society 

 — will not. There is one point, however, I think you have 

 overlooked. You urge the improbability of the required in- 

 fertility being correlated with the particular variations which 

 characterised each incipient species. But the whole point 

 of my argument is, that the physiological adjustments pro- 

 ducing fertility are so delicate that they are disturbed by 

 almost any variation or change of conditions — except in the 

 case of domestic animals, which have been domesticated 

 because they are not subject to this disturbance. The whole 

 first half of the chapter is to bring out this fact, which 

 Darwin has dwelt upon, and it certainly does afford a found- 

 ation for the assumption that usually, and in some consider- 

 able number of individuals, variation in nature, accompanied 

 by somewhat changed conditions of life, is accompanied by, 

 and probably correlated with, some amount of infertility. 

 No doubt this assumption wants proving, but in the mean- 

 time I am glad you think that, granting the assumption, I 

 have shown that Natural Selection is able to accumulate 

 sterility variations. 



That is certainly a step in advance, and we cannot expect 



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