1896.] 1 < *) [Ortmaiiii. 



due to the form in which Darwin has given the definition of tliis term. I 

 am confirmed in tliis belief, as the same error is committed again and 

 again. Still very recently, at the last meeting of the German Zoological 

 Society, in the discuss^ion following Elmer's discourse, Ziegler* expressed 

 his opinion tliat no important difference exists between Darwin's natural 

 selection and Pfeffer's ; that it is irrelevant whether one says that the 

 fittest is selected, or that the not fitted are destroyed: both processes have 

 the same or nearly the same result, as may be at once uoderstood by an 

 example he quotes from the breeding of races in domesticated animals. 



But even this reference to man's selection in domesticated animals, and 

 the unconditional comparison of it with natural selection, is the weak 

 point, and apparently the term "selection" used by Darwiuf induced 

 this error. I shall demonstrate here, that both processes, the natural and 

 the artificial, are certainly not identical, although apparently similar, and 

 especially that the final results of both are entirely different. It is true, 

 Darwin himself avoided this mistake,:]: but it was certainly made by sub- 

 sequent authors, and especially Weismann must have fallen into it, since 

 his odd misinterpretation of natural selection could otherwise hardly be 

 intelligible. 



Weismann apparently has reasoned in the following manner. Natural 

 selection etfects that individuals possessing certain useful characters are 

 preserved ia the struggle for existence, and man's selection in domesti- 

 cated animals has a similar eflfect, preserving individuals provided with 

 certain characters desired by the breeder. Consequently both processes 

 are completely identical, with the only modification, that in the first the 

 principle of utility is ruling, in the second the wishes of man. Fartiier, 

 since in domesticated animals a great number of varieties or races are 

 often obtained from a single original species, and since these races do not 

 differ in their morphological differentiation from natural species, and 

 indeed are perfectly analogous to the latter as regards their relation to the 

 ancestral forms, it was believed that the natural species originated 

 exactly in the same manner, that is to say, since under domestication 

 different races are obtained by man's selection, iu nature different species 

 are formed by natural selection. By this argument, I believe, Weismann 

 came to the view, that species are formed by natural selection alone, and 

 although this opinion of the complete parallelism of natural and man's 

 selection is nowhere explicitly given in his writings, we have to infer it.§ 



*See Verhandl. deutsch. Zoolog. Qeselisch., 1.895, p. 129. 



t Darwin, Origin of Species, 6th ed., 1878, p. 49 : "I have called this principle, by which 

 each slight variation, if useful, is preserved, by the term Natural Selectiou, in order to 

 mark its relation to man's power of selection." Comp. also p. 65, ibid. 



t It is well to be noted that Darwin did not commit this mistake, and that he always 

 regarded natural selection only as taking part in the formation of species, but not as 

 the only cause of it. This is already amply demonstrated by Romanes (" The Darwinism 

 of Darwin and the Post-Darwinian Schools," The Monist, Vol. 6, Xo. 1, October, 1895, p.3ff.,. 



g I do not know whether I have succeeded in trying to fbllow Weismann's thoughts, 

 but I confess fieely : if he did not reason as I have conjectured above, I am at a loss to 

 understand him at all ou this point. But if the latter is the case, I do not think it is a 

 fault of mine. 



PROC. AMER. PHILOS. SOC. XXXV. 151. W. PRINTED SEPT. 4, 1896. 



