19S 



PHYSIOLOGICAL GENETICS 



experimentation demonstrates exactly the same thing as was 

 derived by Goldschmidl from genetic experimentation. 



Furthermore, in this case, a number of facts may bo coordi- 

 nated. 



1. The symmetry field may 

 be enlarged and narrowed by 

 temperature shocks at definite 

 and different sensitive periods 

 (sec Fig. 7, page 21). 



2. The same effect may be 

 produced by a mutant gene. 



3. The shifting effect upon 

 the bands by destruction of 

 wing tissue can be obtained 

 best at the time of the sensitive 

 period for narrowing the sym- 

 metry field (48- to 60-hr. 

 pupa). Heat, as well as the 

 gene Sy, acts by affecting quan- 

 titatively the course of the 

 determination stream. This 

 course may be directed by con- 

 trolling the quantity of the 

 determining substance, the time 

 of its flow, or the limits that 

 may prevent further expansion 

 (which Goldschmidt had called 

 the conditions of the system). 

 Kuehn and Henke speak of force 

 of expansion and force of resist- 

 ance (of and to the stream) 

 which is the same as quantity 

 or time of flow of the determin- 

 ing stuff and the conditions of 

 the system in Goldschmidt 's old 



terminology. It might finally be added that Kuehn and 

 Engelhardt (1936) performed the same type of experiments upon 

 the currant moth, Abraxas grossulariata, with practically the 

 same results aside from minor differences in detail. 



Fig. 37. — Right pupal wings of flour 

 moths, black race, operated in pupae 

 (0 to 24 hr. age). (From Kuehn and 

 Henke, 1936, Abh. Ges. Wiss. Goettingen, 

 15, Fig. 96.) 



