172 PHYSIOLOGICAL GENETICS 



4. Bach factor competes for this source in terms of its potential 

 units. The total pigment production depends upon the propor- 

 tion and power of interaction of all factors. 



5. V governs production of yellow flavone; 7, the ivory flavono 

 apigenin. // reduces the potential value of )'. 



6. In the presence of A and B, cyanin is produced if the total 

 potential units are below 8; and pelargonin, if they are above 8. 



7. Tentatively these actions in terms of units are related 

 to the constitution of the pigment molecule by assuming that they 

 are involved in controlling the oxidation of the phenyl ring. 



There is no doubt that in this fine piece of work a considerable 

 step has been made toward interpreting the interaction of genes 

 in terms of the interplay of chemical reactions. In doing so, the 

 same types of principles were found at w-ork as in the other cases 

 that we reported : reaction velocities, proportional effect of gene 

 quantities, threshold conditions, competitive actions (see sex- 

 determining reactions, page 52). The system of genie action 

 here revealed is then the same as postulated in Goldschmidt's 

 theory of reaction velocities in tune, as the authors also indicate. 



We may state finally that it would be desirable to have more 

 information regarding concrete types of reaction and the exact 

 nature of their interplay. What little is known in this respect 

 will be reported in a special chapter. Attention should be called 

 finally to some cases in which the disturbance of the proper tuning 

 of reaction can be described in relation to definite processes. 

 Goldschmidt has discussed, in a number of papers since 1920, the 

 many beautiful examples of this kind furnished by the facts of 

 intersexuality. The simplest and clearest is the following: The 

 end of morphogenesis of the organs of insects is given by the 

 process of chitinization of the soft organs, and normally this occurs 

 when development is completed. In intersexes, numerous organs 

 start development at a later date than normal, with the conse- 

 quence that at the time of chitinization a developmental stage 

 or even an imaginal disk is present where a completely developed 

 organ should be. In this case, the embryonic structure is being 

 chitinized and appears thus in the adult. Here the effect is 

 produced genetically by the improper balance of the reactions 

 controlled by female and male determiners together with the 

 unchanged general reactions of development. It is an actual 

 disturbance of tuning. 



