136 ON VARIABILITY AND ADAPTATION 



developed possessing criminal features. However much a man 

 abuses his soma, or body, is of little moment ; the effect upon 

 the offspring is minimal. 



I put this in strong language and baldly, and it may be 

 urged that I exaggerate the state of affairs. I do not think 

 I do. I believe that in making this statement I but give 

 expression to the general, if confused, ideas of the majority : 

 nay, more, that I state the received conception of what Weis- 

 mann's theory means when applied to man and to abnormal 

 inheritance in man. 



Now, if there is one conclusion to which we think experience 

 surelv leads us as medical men, it is that the sins of the father do 

 tend to be visited upon the children even mito the third and fourth 

 generation. We think we see this demonstrated day after day. 

 But Weismann does not support this view. It is true that if we 

 study Weismann we find that he does not state this in so many 

 words ; he admits 1 that the germ plasm is not absolutely 

 unchangeable, that the nutrition and growth of the individual 

 must exercise some influence upon its germ cells, " but in the 

 first place this influence must be extremely slight, and in the 

 second place it cannot act in the manner in which it is usually 

 assumed to take place." Certainly he does not make it clear 

 that he believes in the distinct transmission of any order of 

 acquired characters. 



Weismann's Theory. — Weismann, I need scarce say, explains 

 inheritance along the following lines : the germ plasm, the 

 essential matter of the fertilized cell from which the individual 

 develops, must in the process of fertilization come to contain 

 portions of the germ plasm of both father and mother, brought 

 to it by the nuclear material of the ovum and spermatozoon 

 respectively, and the germ plasm of the father and mother 

 must contain portions of the germ plasms of paternal and 

 maternal grandfathers and grandmothers. And so, going back 

 through a long series of generations, it follows, according to him, 

 that representatives of the germ plasms of a long series of 

 ascendants, or progenitors, are contained in the nuclear material 

 of each ovum and spermatozoon. The constitution of a germ 

 cell therefore may be represented, for purposes of inheritance, 



1 Weismann, On Heredity. Authorized translation by Poulton, Schonland, 

 and Shipley, Oxford, 1889, p. 170. 



