Introduction 425 



of the phenomenon of intersexuahty and its separation from gynandro- 

 morphism, which permitted giving the sex chromosome mechanism 

 a genetical and a functional meaning expressed in the quantitative or 

 balance theory of sex determination ( Goldschmidt, 1911-1920). The 

 basic point was that definite conditions between the sexes, that is, in- 

 tersexuahty, could be produced at will by proper genetic combinations 

 (crosses of subspecies of Lymantria dispar) without any change in the 

 mechanism of the sex chromosomes, and this in a typical quantitative 

 series from the female through all intergrades to the male, and from 

 the male through all intergrades to the female, with sex reversal in 

 both directions at the end points. The consequence was: (1) the old 

 assumption that each sex contains the potentiality for the other sex 

 was proved to be the result of the presence of both kinds of genetic 

 sex determiners in either sex; (2) the existence of a quantitative rela- 

 tion, later termed "balance" (though it is actually an imbalance), 

 between the two types of sex determiners decides sexuality, that is 

 femaleness, maleness, or any grade of intersexuahty; (3) one of the 

 two types of sex determiners (male ones in female heterogamety, 

 female ones in male heterogamety) is located within the X-chromo- 

 somes, the other one, outside of them; (4) as a consequence of this, 

 the same determiners of one sex are faced by either one or two por- 

 tions of those of the other sex in the X-chromosomes; (5) the balance 

 system works so that two doses in the X-chromosomes are epistatic to 

 the determiners outside the X, but one dose is hypostatic; (6) inter- 

 mediate dosage (or potency) conditions in favor of one or the other 

 of the two sets of determiners result, according to their amount, in 

 females, males, intersexes, or sex-reversal individuals in either direc- 

 tion; (7) the action of these determiners in the two sexes can be 

 understood in terms of the kinetics of the reactions controlled by the 

 sex determiners, namely, by the attainment of a threshold of final 

 determination by one or the other chain of reaction in early develop- 

 ment; while in intersexuahty the primary determination, owing to the 

 1X-2X mechanism, is overtaken sooner or later — meaning in higher or 

 lower intersexuahty — by the opposite one, so that sexual determination 

 finishes with the other sex after this turning point. The last point is, of 

 course, a problem of genie action. 



These basic facts, which have since been established in all other 

 comparable cases, pose a series of problems. Where are the deter- 

 miners outside the X-chromosomes located? Do diflFerent types of these 

 locations exist? How is the mechanism of balance influenced by 

 genetic or external environment? In what way does the balance mech- 



