v.] IN THE THEORY OF NATURAL SELECTION. 275 



sented somewhat as follows. The phenomena of heredity lead 

 to the conclusion that each organism is capable of producing 

 germs, from which, theoretically at least, exact copies of the 

 parent may arise. In reality this is never the case, because 

 each organism possesses the power of reacting on the different 

 external influences with which it is brought into contact, a power 

 without which it could neither develope nor exist. Each organ- 

 ism reacting in a different way must be to some extent changed. 

 Favourable nutrition makes such an organism strong and large ; 

 imfavourable nutrition renders it small and weak, and what is 

 true of the whole organism may also be said of its parts. Now 

 it is obvious that even the children of the same mother meet 

 with influences different in kind and degree, from the very be- 

 ginning of their existence, so that they must necessarily become 

 unlike, even if we suppose them to have been derived from ab- 

 solutely identical germs, with precisely the same hereditary 

 tendencies. 



In this manner individual differences are believed to have 

 been introduced. But if acquired characters are not transmitted 

 the whole chain of argument collapses, for none of those changes 

 which are caused by the conditions of nutrition acting upon 

 single parts of the whole organism, including the results of 

 training and of the use or disuse of single organs, — none of 

 these changes can furnish hereditary differences, nor can they 

 be transmitted to succeeding generations. They are, as it were, 

 only transient characters as far as the species is concerned. 



The children of accomplished pianists do not inherit the art 

 of playing the piano ; they have to learn it in the same laborious 

 manner as that by which their parents acquired it ; they do not 

 inherit anything except that which their parents also possessed 

 when children, viz. manual dexterity and a good ear. Further- 

 more, language is not transmitted to our children, although it 

 has been practised not only by ourselves but by an almost 

 endless line of ancestors. Only recently, facts have again been 

 worked up and brought together, which show that children of 

 highly civilized nations have no trace of a language when they 

 have grown up in a wild condition and in complete isolation '. 

 The power of speech is an acquired or transient character : it 



* Compare Rauber, ' Homo sapiens ferus oder die Zustiinde dcr Vcr- 

 wilderten.' Leipzig, 1885. 



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