Weismanris theory of Heredity (1891). 55 



quent ontogenetic stages are supposed to be ultimately 

 derived from this idio-plasm of the first stage, it is 

 evident that the particulate differences in question 

 must already have been present in the so-called 

 " undifferentiated idio-plasm of the first ontogenetic 

 stage." Unless we are to have a mere juggling with 

 words, we cannot put into our successive idio-plasms 

 any particles of kinds differing from those which are 

 contained in the original germ-plasm. Therefore I 

 say that, notwithstanding this change of terminology, 

 Weismann must continue to assume, as the material 

 basis of heredity, ultimate particles of germ-plasm 

 which are already differentiated into as many diverse 

 categories as there are differences between the parts 

 of the resulting soma — although, of course, these 

 ultimate particles need not be nearly so numerous in 

 each of their categories as they afterwards become by 

 self-multiplication while forming each of the resulting 

 tissues. 



But this is precisely what the theory of pangenesis 

 supposes ; so that I see no reason why these ultimate 

 particles of germ-plasm should not be regarded as 

 "gemmules," so far as their size, number, and function 

 are concerned. In point of fact, they differ from 

 gemmules only in respect to their origin : they are 

 not particles derived from somatic-cells of the preceding 

 generation, but particles derived from germ-plasm of 

 the preceding generation. Or, to state the difference 

 in another form, if we regard the sexual elements as 

 constituting the physiological centre of the organism, 

 then the theory of germ-plasm supposes these ultimate 

 carriers of heredity to originate at this centre, and 

 then to travel centrifugal \y ; while the theory of pan- 



