Introduction 249 



and "hormones" would turn out to be amino acid precursors of 

 melanin, just as it had been known for a long time for tyrosin and 

 dopa. This is exactly what occurred. 



The reason for insisting on this discussion is that, in my opinion, 

 the wrong terminology is deceptive and dangerous. Thus the great 

 chemist Butenandt glorifies the discovery of Genwirkstoffe in papers 

 read by chemists and general readers (e.g., 1952), who are led to 

 believe (as the author does himself, who as a chemist takes his 

 biological terminology from the biologist) that definite active sub- 

 stances have been isolated by which the genes control development. 

 Actually, only one step (or more) in the consecutive synthesis of a 

 chemically comphcated, depository product of the organism ( melanin ) 

 has been elucidated by the analysis of an intermediate product, a 

 precursor. The brilliant work by the aforementioned pioneers is in no 

 way minimized by the demand for a terminology which does not raise 

 the meaning of the facts to a plane where it does not belong. 



While the genetic and biochemical analysis of pigment precursors 

 cannot be used as an example for our theory ( 1917a, 1920a ) of genie 

 action through production of morphogenetic "hormones," the general 

 idea seems unavoidable, whether these "hormones" are real hormones 

 or enzymes or inductors or definable substances hke DNA or RNA. 

 Within the simple frame of the generalized system of action — to 

 which the cytoplasmic substrate also belongs — the details of genetic 

 control of development are to be understood by the interplay of 

 timing, order, velocities, competitions, and threshold conditions of 

 these reactions, what I called their attunement, together with the 

 movements and distribution of the substrates and products and the 

 threshold conditions present for each individual step, which means 

 the same dynamically as the term "genie balance" expresses statically. 

 It should, of course, be called "balance of genie actions." "Genie 

 balance" involves the same type of error ( discussed above ) as does the 

 term "plasmon-sensitive genes" ( to be discussed again below ) . Within 

 such a system a great many details of gene-controlled processes above 

 the level of direct and simple biochemical synthesis can be described 

 adequately. In the end, the question of the special biochemical mean- 

 ing will always appear, and biochemical genetics will take over 

 wherever there is a chance. Unfortunately, at present such a chance 

 exists only for stuflFs deposited somewhere in the body, like pigments 

 in animals and plants or end products of metabolism, and for blocks, 

 of whatever origin, to synthesis of amino acids and vitamins and 



