Discontinuity 371 



The Paradox of Change 



With Darwin and his predecessors this was not an im- 

 portant distinction. Heredity used to be considered a 

 " force " that somehow made the offspring resemble their 

 parents, more or less, not a process for which we could ex- 

 pect to find the causal mechanism, at least not in the near 

 future. We have seen that August Weismann made the 

 distinction between characters that are heritable, because 

 they are determined by something in the germ plasm, and 

 those that are not heritable, because they appear in the body 

 under the influence of environmental conditions (page 310). 

 Weismann went farther and declared that those departures 

 from the parental type which had their origin in the ger- 

 minal material, are transmitted, whereas those variations 

 from the norm which had their origin in the body or soma 

 plasm are not inherited. He did not pretend to know how 

 germinal changes come about, although he speculated and 

 theorized profoundly on the problem. Indeed, his distinc- 

 tion between the germ plasm and the soma was largely a 

 theoretical one, and we did not know until many years later 

 that Weisrnann had hit upon an essential point. 



It is difficult to imagine how new characters can origi- 

 nate in germinal changes. The same difficulty is presented 

 by the general question of transformation of species, namely, 

 the paradox of discontinuity. If the germ plasm has been 

 continuous and unchanged for generations, if it has been the 

 very foundation of stability for a species, in spite of fluctu- 

 ating conditions and in spite of modifications impressed upon 

 the bodies of millions of individuals, how can it suddenly 

 acquire anything new? Weismann himself insisted most 

 vehemently that nothing could happen to the germ plasm. 

 Yet something must have happened to it (according to the 

 theory) if evolution is to take place. 



The opponent of the evolution idea cannot conceive 

 how parents of one species can give rise to an individual that 

 is of a different species. The evolutionist cannot conceive 



