Wcisni ami's Ancestral Plasms 53 



ena are explained by Spencer in a similarly simple 

 manner. 



Spencer's theory has, without doubt, the advantages 

 of a clear and concise system. But it does not take into 

 account the train of thought developed in our first section. 

 On the basis of those general considerations, therefore, 

 the theory is insufficient. Especially can it not explain 

 in a satisfactory manner the differentiation of organs, and 

 any attempt to bring it into accord with this process 

 would prove its fundamental inadequacy. Since the same 

 thing is likewise true of Weismann's theory of the ances- 

 tral plasms I refer the reader, in regard to it, to the con- 

 clusion of the next Section. 



6. Weismann's Ancestral Plasms 



In a series of thoughtful writings during the last 

 decade, August Weismann has aroused the general in- 

 terest of the scientific public in the principles of heredity. 

 In doing so, he used, as a basis, the most recent achieve- 

 ments in the domain of cell-theory and the process of 

 fertilization. 



Proceeding from the conviction that the development 

 of children from material particles of their parents is the 

 cause of heredity, and that the solution of the great 

 mystery is, in truth, to be looked for in the molecular 

 structure of the protoplasm, he tries to form a definite 

 conception of this structure. He begins by saying that, 

 in lower organisms, which do not possess a sexual dif- 

 ferentiation, the germ-plasm of each individual must 

 still be completely uniform. During fertilization, how- 

 ever, a mixing of the two parental germ-plasms must take 

 place, and thus in the child there are mixed two, in the 



