1^0. 644] ABBE ST ED EVOLUTION 



271 



ent ways, by the genes; and not only through internal 

 factors, as claimed by the Neo-Darwinian school, but 

 also through external ones as demanded by the Neo-La- 

 marckians. The genes, which are not only actual units, 

 or representatives of definite phenotypic characters, but 

 definitely delimited, material bodies, may not only pro- 

 duce new characters or character-combinations by a cor- 

 relative and a combinative mode of ontogenetic evolution, 

 or by loss of genes, as demonstrated by abundant experi- 

 ments, but undoubtedly there takes place also a new for- 

 mation of genes in evolution. This they hold to come 

 about in successive stages through long enduring ex- 

 ternal influence, which first acts upon the cytoplasm of 

 the cells and especially of the germ-cells. This cyto- 

 plasm in itself has been proven to have certain hereditary 

 possibilities (plasm ogenous heredity). Under long per- 

 sistent external influence there form first preliminary 

 stages of genes in the cytoplasm which finally, when a 

 certain "threshold" (Schwelle) of continued strain is 

 passed, become true genes of the lieredity-chromatin. 

 "When this takes place, mutations appear abruptly (salto- 

 mutations). 



This view, here altogether too briefly presented, would 

 explain the absence of evolution through salto-mutations 

 in cases of persistence under continued stable exterior 

 conditions, and since the cytoplasm is known also to in- 

 fluence directly the heredity-chromatin, also the absence 

 of flucto-mutations or variations under stable conditions 

 through lack of external stimulation. 



However, in the cases where no new genes are formed 

 by external influences, new characters could still appear 

 through loss of genes or correlative or combinative modes 

 of production of new genes from the old ones within the 

 germ-plasm. This, however, leads to a restrictive cone 

 of divergence {" Streuung ") of the characters and 

 through " self-differentiation " by a combinative mode 

 of gene-production to the excessive characters of many 

 terminal series {e.g., dinosaurians) ; and to the rigid 



