The Germ Plasm 313 



posed this interpretation: It is the germ cell that gives rise 

 to an individual body, not the individual to germ cells. It 

 is false to say that a plant or an animal produces eggs 

 or sperms, the q^^ or sperm plasma is already present 

 at the birth of the individual (see Fig. 83). Accord- 

 ing to this view, the germ plasm is continuous and the 

 soma is in each generation an offshoot or branch from this 

 immortal stream of life. The living matter of the individ- 

 ual is unable itself to continue the species, but it serves 

 as an instrument for the germ plasm, shielding it and 

 supplying it with nourishment and an opportunity to 

 multiply. 



When Weismann proposed this theory he was unable 

 to say definitely whether or not the germ plasm does actually 

 behave in developing individuals in accord with this sup- 

 position. Rudolf Virchow, the anti-evolution pathologist, 

 had already shown, even before the publication of The Origin 

 of Species, that there is a continuous cell-lineage in the 

 development of the body, and not, as earlier observers had 

 supposed, a formation of cells around dispersed centers of 

 organization. The cells are related to one another. The 

 continuity of the germinal protoplasm had been announced 

 by various students, but the significance of this continuity 

 was first pointed out by Weismann on purely theoretical 

 grounds. It has since been shown that in many plants and 

 animals a " germinal track " does actually become separated 

 early in the development, and that it remains distinct from 

 the body cells to the time of sexual maturity (Fig. 84) . At 

 any rate, as the theory became clarified, it set up an insuper- 

 able obstacle to the acceptance of the doctrine of inheritance 

 of acquired characters, for Weismann's theory left no place 

 for a mechanism whereby the changing soma could influence 

 the germ plasm. The individual is like the parent, accord- 

 ing to Weismann, not because the parent has molded the 

 germinal material in his own likeness, but because the parent 

 and the offspring both derive from the same stream of con- 

 tinning germ plasm. 



