The interrelation of genetic and non-genetic factors 



in development 



by Arend L. Hagedoorn, Ph. D. 



Verrieres le Buisson. 



The work of Mendel has placed the study of development 

 on a new and solid basis. From his work and that of his followers 

 we have at last learned to distinguish between the two kinds of 

 factors in the development of the organisms, so that we may 

 now study them separately, and find out what part each cathegory 

 plays in ontogenetic development, and in how far each can have 

 furnished the material for a phylogenetic development of the 

 different types. 



The object of this paper is to treat of the differences 

 between the two sorts of factors in development, to point out 

 their relation, and the possibilities in Controlling this relation in 

 some organisms for economic purposes. The lack of knowledge 

 concerning the parts played by the genetic, transmitted factors 

 on one hand, and the environment, the non-genetic factors on the 

 other, in the development of the organisms, in pre-Mendelian times 

 is very well illustrated by the Opposition of the views of Oscar 

 H e r t w i g and Weismann on the subject. Weismann, building 

 forth on Darwin's conception of evolution as caused by selection on 

 small differences, individual Variation, has elaborated a vast 

 complex of theories, concerning the Constitution of the „germplasm", 

 numerous living, protoplasmic particles of different sorts, each 

 mysteriously calling forth one special organ or tissue. Parting 

 from the altogether justified consideration that the effects 

 of the environment on the individual are not transmitted, he 

 has tried to ascribe the whole ontogenetic development to 

 transmittable, genetic causes, neglecting the direct importance of 

 the environment for this development. Oscar Hertwig on the 

 other hand, realizing the enormous importance of all kinds of 

 non-genetic factors for all the developmental processes, has gone 



