52 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



development of the organism), we axe at once con- 

 fronted with a question of crucial importance to 

 biology. Are these traces derived from the trans- 

 mission and accumulation of experiences (amount- 

 ing to characteristics) which have happened to the 

 ancestors, or are they derived directly from the 

 germ plasma of the ancestors by its direct continuity 

 and without the intervention of influences from the 

 body cells ? In other words, are we to believe that 

 acquired characters are transmitted or not ? There 

 are two leading hypotheses on this subject that lay 

 claim to our attention. The one which denies that 

 acquired characters are transmitted is known as 

 Weismann's hypothesis. The one which maintains 

 that acquired characters are transmitted is known as 

 the Lamarckian theory, or, in its modern form, as the 

 mnemic or Hering-Semon hypothesis, According to 

 the hypothesis of Weismann the racial or phyletic 

 life of all organisms is pictured as a connected and 

 continuous chain of germ cells. In order that the 

 chain should continue unbroken, it is essential that 

 the germ cells should be housed and nourished in 

 the body, or soma, of a full-grown individual in each 

 generation. But this body, or soma, be it noted, 

 contributes nothing to the properties of the germ 

 cells. The germ cells may vary spontaneously from 

 generation to generation, but the soma in which 

 they are sheltered is quite without influence over 

 them in respect to inheritance. Therefore, accord- 

 ing to this hypothesis, no characters which are 



