286 Theories Treating of Inheritance 



end the acceptance of these germs has led necessarily to 

 systems which reject the inheritance of acquired char- 

 acters concur to prove, although more proof is certainly 

 no longer necessary after all the other considerations 

 which we have developed in an earlier chapter, that the 

 very idea of these preformistic germs is untenable, as is 

 thus every theory founded upon them. 



However limited the number of theories or hypoth- 

 eses selected by us, and however rapid and brief the 

 critical exposition which we have made of them, it seems 

 to us nevertheless that it is unnecessary to proceed further 

 with our examination. For it has shown us that among 

 the principal theories, which up to the present have been 

 devised to explain the inheritance of acquired characters, 

 none has accomplished this difficult task, and it has 

 already served another purpose for which chiefly we 

 undertook it. This purpose consisted on the one hand in 

 bringing to light in other theories the most suggestive and 

 fruitful ideas put forward; on the other hand in deter- 

 mining the conditions which are necessary and sufficient 

 to render possible the inheritance of acquired characters, 

 and a critical examination of concrete theories already 

 developed has certainly helped to put these conditions in 

 evidence better than simple reflection upon them could 

 have done. 



If we take a look over the road which we have thus far 

 traveled we see that among these conditions those which 

 have appeared to us as the essential and fundamental ones 

 are the three following: 



I. All the manifold physical, chemical, morphologi- 

 cal, and physiologic variations, which can appear in the 

 most different parts of the organism, are to be ascribed 



