Primary Genetic Possibilities 427 



his material where the trigger action is assumed to involve partly the 

 Y-chromosome. This means that the balance idea is discarded or 

 used only in explanation of some minor features. 



This interpretation, which does not work when applied to indi- 

 vidual cases and assumes what I would call a naive genetic idea, has 

 two different aspects. One is the assumption of individual genes for 

 every possible character, which in the case of sex would mean for 

 every female and male character, extending in some cases to each 

 cell of the body ( a naive or even primitive concept ) ; and the other is 

 the trigger idea. Since the first part of the interpretation enters all 

 other genetic theories, we may dispose of it first. I myself started with 

 this assumption when in my early work (1911Z?, 1912) I assumed the 

 presence of a set of genes for secondary sex characters, which I called 

 A and G, and assumed that they were linked with the real sex deter- 

 miners. I gave up this idea when it turned out that in intersexuality 

 all characters behave in a parallel way to those in the separate sexes 

 themselves, with definite rules. Thus I concluded that sexual differ- 

 ences, extending to differences in practically every cell, are not based 

 upon two sets of genes for male and female development, sometimes 

 called the sex-promoter genes; but that any genetically controlled 

 character may have an alternative norm of reaction which is decided 

 by the real primary sex-determining mechanism. There are many 

 facts available to prove the correctness of this assumption. Differences 

 of this type in the two sexes may mutate individually, with the result 

 that after crossing the mutant with the original form a simple Men- 

 delian segregation occm-s, but only in the proper sex; that is, mutants 

 of male characters segregate only in the male. (I called this sex-con- 

 trolled inheritance; details in my book 1920Z?, and a recent discussion, 

 1953a. ) The best illustration of the interpretation is found in Lyman- 

 tria dispar. The male has dark wing color and the female a whitish 

 one. Mutants of the male color exist which Mendelize simply in the 

 males but do not affect the females. However, if these females become 

 intersexual, in specific experiments, they show the same segregation 

 of wing color as the males. Since these intersexes are of the lowest 

 grade, being actually fertile females with only male wing color and 

 partly male antennae, the sex-deciding mechanism is hardly affected. 

 It is very difficult to imagine that only the wing-color gene and its 

 mutant of the male type are picked out for enhancement with sup- 

 pression of its female partner, while everything else remains female. 

 It is simpler to assume that wing color in both sexes is determined by 

 the same genetic determiners, which act with an alternative norm of 



