246 Theories Treating of Inheritance 



conception of a mechanism for the inheritance of acquired 

 characters. Even if the hereditary substance should be 

 preserved in its entirety, and unaltered, in the nuclei of all 

 cells without exception throughout development, this 

 would be ascribable only to qualitatively equal nuclear 

 division. But one could not but ask why the modifica- 

 tions which supervene in the hereditary nuclear substance 

 of such and such somatic cells in consequence of a new 

 local functional adaptation in the adult stage should not 

 remain limited to these cells alone. 



Very noteworthy, however, in Driesch's theory is the 

 conception that ontogeny takes place by means of a series 

 of successive liberations of different energies remaining 

 up till then in the potential state, and also that one result 

 of the liberation of each of these energies and of the 

 effects which it produces is that the necessary and 

 sufficient conditions for the liberation of the next follow- 

 ing potential energy are brought about. 



Herbst 



The epigenetic conception of Herbst is still less 

 capable if possible, than that of Driesch of rendering con- 

 ceivable any mechanism whatever for the inheritance of 

 acquired characters. 



He mentions at first several experiments upon the 

 way in which unicellular organisms and cells react to cer- 

 tain stimuli, and also a great number of facts serving to 

 show the great dependence of plant ontogenies especially 

 upon external influences. While it is evident that 

 external influences constitute most often only liberating 

 or releasing stimuli, they seem on the contrary to become 

 in certain formations real formative stimuli. In these 

 formations there is involved not only a true ontogenesis 



