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 
