PART IV 



THE TRANSFORMATION OF SPECIES: ITS 

 ORIGIN IN THE IDIOPLASM 



CHAPTER XIII 



THE SUPPOSED TRANSMISSION OF ACQUIRED 

 CHARACTERS 



I. Difficulties in the Way of a Theoretical Basis 

 FOR THIS Assumption 



By acquired characters I mean those which are not performed 

 in the germ, but which arise only through special influences 

 affecting the body or individual parts of it. They are due to 

 the reaction of these parts to any external influences apart from 

 the necessary conditions for development. I have called them 

 *■ so7natogenic'' characters, because they are produced by the 

 reaction of the body or soma, and I contrast them with the 

 ' blastogenic ' characters of an individual, or those which origi- 

 nate solely in the primary constituents of the germ (' Keimesan- 

 lagen'). It is an inevitable consequence of the theory of the 

 germ-plasm, and of its present elaboration and extension so 

 as to include the doctrine of determinants, that somatogenic 

 variations are not transmissible, and that consequently every 

 permanent variation proceeds from the germ, in which it must 

 be represented by a modification of the primary constituents. 



I will first attempt to show how this conclusion is arrived at 

 theoretically, and will then proceed to test it by ascertaining 

 how far it is in agreement with actual observation, and whether 

 the theory can be justified by facts. 

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