Correspondence on Biology, etc. 



but I find it quite impossible for me to follow their de- 

 tailed studies and arguments. It wants a mathematical 

 mind, which I have not. 



But on the general relation of Mendelism to Evolution 

 I have come to a very definite conclusion. This is, that it 

 has no relation whatever to the evolution of species or higher 

 groups, but is really antagonistic to such evolution I The 

 essential basis of evolution, involving as it does the most 

 minute and all -pervading adaptation to the whole en- 

 vironment, is extreme and ever-present plasticity, as a 

 condition of survival and adaptation. But the essence of 

 Mendelian characters is their rigidity. They are trans- 

 mitted without variation, and therefore, except by the 

 rarest of accidents, can never become adapted to ever- 

 varying conditions. Moreover, when crossed they reproduce 

 the same pair of types in the same proportions as at first, 

 and therefore without selection; they are antagonistic to 

 evolution by continually reproducing injurious or useless 

 characters — which is the reason they are go rarely found in 

 nature, but are mostly artificial breeds or sports. My view 

 is, therefore, that Mendelian characters are of the nature 

 of abnormalities or monstrosities, and that the ** Mendelian 

 laws" serve the purpose of eliminating them when, as 

 usually, they are not useful, and thus preventing them 

 from interfering with the normal process of natural selec- 

 tion and adaptation of the more plastic races. I am also 

 glad to hear of your new argument for non-inheritance of 

 acquired characters. — Yours very truly, 



Alfred E. Wallace. 



To Sib W. T. Thiselton-Dier 

 Old Orchard, Broadstone, Wimbome. February 8, 1911. 

 Dear Sir W. Thiselton-Dyer,— I thank you very much for 

 taking so much trouble as you have done in writing your 



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