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PHYSIOLOGICAL GENETICS 



later pattern: parts that later will carry dark pigmented scales 

 show a slower differentiation of the scales than parts that will 

 later carry white or yellow or red scales (distinguished by con- 



Fig. 50. — Pupal wings of the swallowtail, Thais polyxena. a, fully developed; 

 b, before pigment formation, later white parts with finished scales, later pig- 

 mented parts collapsed. (from Goldschmidt, Fig. 48.) 



taining uric derivatives or carotinoids or air). This can be 

 detected only during a very short period of differentiation: if a 

 pupal wing at this stage is dried, the already differentiated scales 

 remain erect; the undifferentiated scales on later dark areas, 

 however, collapse because they are soft bags filled with blood. 



