76 OPT. A CTI I . , HEREDITY AND EN VI RON M EN T 



of chemical transformations) may play a role in biologi- 

 cal phenomena. 



4. Physiological mutations which, in the evolutionary 

 development of an organism, bring about optical inver- 

 sions of the secondary protoplasmic constituents may con- 

 sist in a change of the intermediate "pathways" in a 

 series of reactions. 



5. Protoplasmic systems are provided wdth mechanisms 

 by which "pathways" that would lead to an inversion of 

 the asymmetric structure are avoided. Primary constit- 

 uents of protoplasm are then regulated by a principle 

 called here: ''Principle of fixed pathway". Such mech- 

 anisms do not operate in the transformations of the sec- 

 ondary substances of protoplasm. 



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