2l6 AN INTRODUCTION TO MODERN GENETICS 



heterogamety, the female is MMFF and the male MMFf (often the 

 y =z O as in Drosophila, where the Y is empty). These two pairs of 

 factors act by stimulating the underlying potencies for the two types 

 of differentiation, which are considered by Goldschmidt as two reaction- 

 types of the system as a whole rather than two definite complexes of 

 genes. The stimulations due to the M and F factors are antagonistic to 

 one another, and the result is dependent on whether the M or the F 

 factors are stronger; thus in the case given above the FF factors are 

 stronger than the MM in the female, but the Ff in the male is weaker. 

 Goldschmidt's hypothesis is perhaps more flexible than Correns's and 

 its quantitative character, even though perhaps rather hypothetical, 

 since we do not know exactly what the quantities actually consist of 

 (but see p. 226), nevertheless makes possible more accurate prediction 

 than can easily be attained by Correns's symbolism; it is commonly 

 adopted by zoologists at the present day, but botanists often still retain 

 Correns's formulation. 



I. Lymantria 



Goldschmidt developed his theory from his work of the Gypsy 

 'moth, Lymantria dispar} The moth occurs throughout northern Europe 

 and Asia, and different local races, when crossed, sometimes produce 

 intersexual offspring, as Standfuss first discovered. The moths have 

 female digamety, so their formula in Goldschmidt's notation is $ 

 MmFF, o MMFF. The value of the m factor is O in all the races, and 

 the FF factors, which lie in the autosomes, have the same strength in 

 all races; they therefore have no noticeable effect except in the triploid 

 intersexes, analogous to those in Drosophila (p. 219), with which we 

 are not concerned here. The intersexes arising in crosses between local 

 races depend on variations in the strengths of the M factors and of 

 another female tendency which is not the same as the autosom^al F 

 factors mentioned above, but is inherited through the c5^oplasm. It is 

 symbolized as [7] . 



We must therefore rewrite the formulae of the males and females in 

 terms of the effective factors as [7] MM and [7] M. In the pure races, 

 MM overcomes [7] , which itself overcomes M. The intersexes arise 

 when the balance between [7] and M is such that neither completely 

 overcomes the other. 



Goldschmidt was able to assign different strengths to the M, and 

 ^ Goldschmidt 1931a, 1934, Hammerling 1937. 



