414 



Action of the Genetic Material 



in terms of embryology, that the genie action separating the cubital 

 field with the result of a "raw edge" posteriorly sets in motion the 

 embryonic power of regulation by production of a mirror-image half. 

 This power of regulation is one of the most mysterious properties of 

 development, but a much discussed fact. Here we see it coming into 



B 



Fig. 22. Diagram of wing ( crosshatched ) and thoracic discs (triangles) in a 

 series of stages, explaining change of determination in development of tetraltera. 

 (From Goldschmidt, 1952/?.) 



play as a consequence of a genie action which is just the same as if 

 an experimenter had made a cut between the two embryonic fields, a 

 type of experiment known to set regulative processes into motion in 

 numerous cases studied by experimental embryologists. 



A variant of the preceding features produces the tetraltera type. 

 If the interruption of the quadripartite anlage separates the cubital 



