FOUNDATIONS FOR SEX 



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 point. The consequence was: (1) the 

 old assumption that each sex contains the 

 potentiality of the other sex was proved to 

 be the result of the presence of both kinds 

 of genetic sex determiners in either sex; (2j 

 the existence of a quantitative relation, 

 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 inter- 

 sexuality; (3) one of the two types of sex 

 determiners (male ones in female hetero- 

 gamety, female ones in male heterogam- 

 ety) is located within the X-chromo- 

 somes, the other one, outside of them; (4) 

 as a consequence of this, the same deter- 

 miners of one sex are faced by either one 

 or two portions 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 deter- 

 miners outside the X, but one dose is hypo- 

 static; (6j intermediate dosage (or po- 

 tency) 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 direction; (7) the action of these 

 determiners in the two sexes can be under- 

 stood in terms of the kinetics of the reac- 

 tions 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 development; 

 while in intersexuality the primary deter- 

 mination, owing to the 1X-2X mechanism, 

 is overtaken sooner or later — meaning in 

 higher or lower intersexuality — by the op- 

 posite 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." 



Bridges developed his idea of "genie bal- 

 ance" as a consequence of his observations 

 on chromosomal nondisjunction, particu- 

 larly as it illustrated the loss or gain of a 

 fourth chromosome in modifving nonsexual 



characters. The similarities and contrasts 

 of this view from that of Goldschmidt are 

 indicated by the following quotation 

 (Bridges, 1932) : "From the cytological re- 

 lations seen in the normal sexes, in the in- 

 tersexes, and in the supersexes, it is plain 

 that these forms are based upon a quanti- 

 tative relation between qualitatively differ- 

 ent agents — the chromosomes. However, 

 the chromosomes presumably act only by 

 virtue of the fact that each is a definite 

 collection of genes which are themselves 

 specifically and qualitatively different from 

 one another. There are two slightly differ- 

 ent ways of formulating this relation, one 

 of which, followed by Goldschmidt, places 

 primary emphasis upon the quantitative 

 aspect of individual genes. The other view, 

 followed by the Drosophila workers, em- 

 phasizes the cooperation of all genes which 

 are themselves qualitatively different from 

 one another and which act together in a 

 quantitative relation or ratio. Goldschmidt 

 developed his idea through work with the 

 sex relations in Lymantria and has sought 

 to extend it to ordinary characters. The 

 other formulation, known as 'genie balance,' 

 was developed from the ordinary genetic 

 relations found in characters. Both are 

 crystallizations of fundamental ideas with 

 which the earlier literature was fairly 

 saturated and no great claim to distinctive 

 originality should be ventured for either or 

 denied for one only. Both are physiological 

 as well as genetic — that is, they are formu- 

 lations of the action of genes, not merely 

 statements of the genie constitutions of in- 

 dividuals nor merely studies of the way 

 genes act. The physiological side has been 

 emphasized by Goldschmidt and the ge- 

 netic side by Drosophila workers. But 

 Goldschmidt's tendency to represent the 

 view of genie balance as without, or even 

 as in opposition to, such physiological for- 

 mulation is groundless — as groundless as 

 would be the reciprocal contention that 

 Goldschmidt's theory is only one of 'pheno- 

 genetics.' 



"A common element in the foundation of 

 both formulations is that if a gene is repre- 

 sented more than once in a genotype the 

 phenotypic effect is expected to be different, 

 though roughly in the same direction as be- 



