148 THE THEORIES OF EVOLUTION 



genesis, that is in each of the developing cells, only 

 the determinants which are to control the immediate 

 successive cells are liberated through the specific stim- 

 ulus. 



This is extremely important, for if every cell is 

 practically a germ cell, the distinction between germ 

 plasm and soma plasm is no longer essential. 



By insisting on this distinction, Weismann rejected 

 absolutely the Lamarckian point of view, and his fol- 

 lowers considered it as a refutation of the Lamarckian 

 theory. The question of the inheritance of acquired 

 characters was definitely disposed of. While Weis- 

 mann denied the inheritance of acquired characters, 

 he had to admit certain incontestable facts proving 

 that modifications due to external influences reap- 

 peared in the next generation or generations. This is 

 due, he thinks, to the fact that an influence may bear 

 simultaneously on the soma and the germen; when 

 cold, for instance, modifies the colouring of butter- 

 flies' wings, it acts simultaneously on the determinants 

 of the pigment cells of the wings and on the corre- 

 sponding determinants contained in the sexual cells. 

 We may answer that this concerns only the process of 

 transmission. As transmission remains a fact, it must 

 be conceded that the Lamarckian idea was buried pre- 

 maturely by Weismann. On the other hand, the in- 

 fluence of external factors, which the original Weis- 

 mannian theory considered as nil, comes into its own 



