Potentialities 493 



Potentialities 



The sex chromosomes are undoubtedly factors in the deter- 

 mination of sex, but they alone are not adequate to explain some 

 intersexes and sex reversals. One suggestion that has received 

 considerable support, although in several varying forms, is that 

 all cells have the potentialities for both maleness and female- 

 ness. In some cells the male potentiality predominates, but in 

 others the female potentiality becomes expressed. All the genes 

 for both sexes are present in each cell, although the XY- or ZW- 

 mechanisms result in a difference in the quantitative relation- 

 ships of these genes in different individuals. Thus XX indi- 

 viduals would have more female-tendency genes than XY indi- 

 viduals and, other things being equal, would be female rather 

 than male. In some organisms this strictly quantitative relation- 

 ship is itself not the only important factor. In Lymantria genes 

 for both maleness and femaleness are present, but each type 

 exists in several forms which differ in strength. Strong male 

 genes, combined with weak female genes in an organism that 

 would be female according to its chromosomes, would develop in 

 a male direction and end up a female intersex, whereas weak male 

 genes, combined with strong female genes, might convert an 

 expected male into a female. Goldschmidt has suggested that, in 

 the first example, the organism starts out as a female, but the 

 strong male genes exert such an influence that a "Drehpunkt" or 

 "turning point" is reached, after which the individual develops 

 as a male. The organs or tissues that develop during the earliest 

 stage of ontogeny and right up to the Drehpunkt become female; 

 those that develop after this turning point are male. The inter- 

 sex, then, is not an individual in which every organ and every 

 tissue are intermediate between the two sexes but one in which 

 some organs are wholly female, others wholly male, and some 

 are mixtures of both male and female tissues. In the male type 

 of intersex, the first-formed organs and tissues are male whereas 

 those that develop during later developmental periods are female. 

 A similar explanation has been offered for the triploid intersexes 

 in Drosophila. 



Although all cells may have both male and female potentiali- 

 ties so that organs and tissues may develop in either way ac- 

 cording to the ratio of male-determining and female-determining 



