THE MUTATED GENE 



105 



in which AA and AiA] are the obtained quantities for the char- 

 acter in the two homozygous and AA\ in the heterozygote. 

 Instead of using directly the facet counts, he applies a dynamic 

 view by considering the instantaneous addition of facets. He 

 had found before that the rate of change in mean facet number 

 at any temperature is proportional to the mean facet number at 

 that temperature, i.e., an exponential relation of the formula 

 y = ae rt , in which r is the relative rate of change, t the tempera- 

 ture (centigrade), e the base of the natural logarithms, and a 

 a constant. The instantaneous change in facet number at a 

 given temperature is then expressed by the first derivative: 



dy 

 dt 



yr 



This value he calculates for the different facet numbers at dif- 

 ferent temperatures and different genetic constitutions, and from 

 these values, i.e., the instantaneous change in facet number 

 instead of the direct facet counts, he calculates the coefficient of 

 dominance according to Zeleny's formula. The following table 

 contains the results for the heterozygotes between Full eye, 

 Bar, and Ultrabar for reciprocal hybrids. The second line of 

 headings designates the mothers of the heterozygotes (recipro- 

 cal crosses). 



Table 12 



(From Hersh) 



This shows that the degree of dominance in regard to the 

 number of facets formed at a given moment changes regularly: 

 it decreases in the -f-/Bar case with increase of temperature from 

 dominance of Wild type; it increases for dominance of Ultrabar 



