Endocrine Mechanisms 



731 



of the relationships discussed here are brought together in Figure 278.^^ 



There is substantial evidence that the foregoing gene hormones are used 



up in the reactions in which they are involved, probably entering directly 



Fig. 278. Diagram summarizing the roles of gene hormones and certain other factors in 

 the development of eye pigments in Drosophila. From Ephrussi.^ 



into certain of the reactions involved in pigment production. There seems 

 to be a direct relationship between the quantity of hormone made available 

 and the amount of eye pigment produced. However, since the same hor- 

 mones operating in different insect groups seem to be responsible for the de- 



