428 Genetics of Sex Determination 



reaction according to the presence of the sex-determining stuffs of one 

 or the other sex. 



A powerful support for our interpretation comes from a number of 

 facts concerning environmental action. The antennae of females and 

 males are very different in Lymantria, and the development is also 

 very different from the beginning ( Goldschmidt, 1922). But when 

 females are treated with temperature shocks in a sensitive period of 

 the pupa (Kosminsky, 1909; Goldschmidt, 1922), the antenna be- 

 comes more or less male. Or one part of the genital armature in 

 Lymantria, the uncus, is a single structure developed from a paired 

 anlage. It is homologous to a paired structure in the female genitalia, 

 the labia. In development the first anlagen are paired in both sexes 

 but concresce later only in the male to form the single uncus. If a 

 female becomes intersexual through F/M imbalance, the labia con- 

 cresce into a single unpaired structure of the uncus type. If a male 

 becomes intersexual, one of the first effects is duplicity of the uncus. 

 If a normal male pupa is exposed to temperature shock, the same 

 paired uncus results (Goldschmidt, 1922; Kosminsky, 1927). This 

 might be called a phenocopy of the intersexual condition. Comparable 

 phenocopies in wing color and pattern have been produced by Stand- 

 fuss in pre-Mendelian days and are available also in Lymantria (Gold- 

 schmidt). These facts clearly require an interpretation in terms of an 

 alternative norm of reaction, and cannot possibly be reconciled with 

 the promoting genes and trigger idea, except by rather wild assump- 

 tions. 



Thus the assumption of separate autosomal genes for all individual 

 female and male characters is disproved by the facts of intersexuality 

 as well as by those of phenocopies of sexual characters; this disposes 

 also of the trigger genes and requires a genuine balance system of sex 

 determination plus an alternative norm of reaction. Nevertheless, Cor- 

 rens, followed by Wettstein and Hartmann (see Hartmann, 1943), 

 tried to introduce the "naive" AG system into the balance theory, so 

 that primary sex determination is based upon the F/M balance which 

 simultaneously triggers the inhibition of the mass of A genes and 

 enhances the G group. I think this is an unnecessary complication for 

 which no genetic facts can be adduced, and leads only to making the 

 genetic formulations more onerous. Hence I shall leave the AG sys- 

 tem out of the discussion, under the assumption of an alternative 

 norm of reaction for some or all genetically controlled processes, as the 

 case may be. I shall mention the AG idea only in connection with very 

 specific features of sex determination in plants (where we shall also 



