100 The American Naturalist. [February, 



the " Theory of Germ Plasm " corresponds to the personal in- 

 clinations of its author and is in no sense a logical deduction 

 won by the collation of facts. The assumption of a difference 

 between germ plasm and histogenic plasm explains nothing. 

 Even according to Weismann's own exposition it explains 

 nothing, for the supposed phenomena which the assumption is 

 said to explain, according to Weismann, do not exist. Ac- 

 cording to him, the circumstances are the following : The phe- 

 nomena due to the germ plasm do not occur in somatic cells, 

 therefore they have a different plasm, namely, histogenic; 

 further, these phenomena do occur in somatic cells, there- 

 fore, they have germ plasm. Attention must be directed 

 also, and explicitly, to the fact that Weismann offers no obser- 

 vations to support his fundamental assumption. His theory is 

 mystical to an extreme degree. In Weismann's book, " The 

 Germ plasm," one finds one hypothesis after another in order 

 to support his tottering first hypothesis— germ plasm and his- 

 togenic plasm are special and separate substances. I demand 

 of Weismann that he lay aside all his hypotheses, and present to 

 us solely the facts, which support his theory of germ plasm. 

 Then he will learn, as other investigators have already 

 learned, that his hypothesis has been built up without suffi- 

 cient foundation. 



Let an investigator enquire for a possibility of testing the 

 existence of the " Ids," " Biophors," " Determinants," etc., as- 

 serted by Weismann, and he will discover that the whole 

 fabric is woven by speculative imagination. Confirmation of 

 his ideas has, strictly speaking, not been attempted by Weis- 

 mann. Indeed, confirmation is altogether impossible, for his 

 conceptions are far beyond the limits of present human means 

 of investigation. 



It is time to finally discard a theory which leads astray and 

 which, although it arose without scientific justification, is 

 again and again pushed to the front by its promulgator. It 

 is a scientific duty to take an unhesitating stand against 

 Weismann's theory, for only so can it become known that 

 those who have specially occupied themselves with the 

 problem of heredity reject Weismann's theory of germ plasm 

 unconditionally. 



