SEX SPECIFIC ACTION OF HORMONES 311 



The embryos were dissected at about two weeks after im- 

 plantation. "Whenever the grafts exhibited a good growth 

 the embryos were affected, but when the grafts grew sHghtly 

 or not at all the resulting embryos were nearly normal or 

 apparently not affected." By affected embryos Minoura 

 means those in which male and female characters were present 

 simultaneously. Whereas both Miillerian ducts completely 

 disappear in the normal male embryos in the third week of 

 incubation, there were in the experiments of Minoura embryos 

 with testicular grafts, having gonads in siiti of the male 

 type and at the same time Miillerian ducts; or there were 

 embryos with testicular grafts, having gonads of the female 

 type, but with a deviation from the normal, in as much 

 as the right gonad also developed, and at the same time the 

 Miillerian ducts were not differentiated to the normal extent; 

 in many cases where testicular grafts were made Wolffian 

 ducts more or less of the male type were present simultaneously 

 with Miillerian ducts. On the other hand embryos with ovarian 

 grafts revealed gonads of the male type with Miillerian ducts 

 partially differentiated as in the female, or gonads of the 

 female type with Wolffian ducts more of the male type. 

 Where the engrafted gonad was a testis, the Miillerian ducts 

 were undifferentiated and showed signs of degeneration. 

 Where the grafted gonad was an ovary, the Miillerian ducts 

 were retained, degenerative changes in the ducts were absent, 

 and the left duct was better developed and more differentiated 

 than the right one. It is naturally impossible to say to which 

 sex the individual egg originally belonged. But there are some 

 indications as to this. The presence and degree of differentia- 

 tion of the Miillerian ducts in embryos with testicular grafts 

 and gonads of the male type can be only explained by the 

 assumption that these embryos originally developed and 

 differentiated to a certain extent in the direction of femaleness 

 but that their original ovaries became transformed under the 

 influence of the testicular graft into gonads of the male type. 

 Minoura rightly concludes from his experiments "that the 

 sexual characters are reversible and that these characters 

 after having differentiated to a certain extent in the direction 

 of one sex may be altered and modified in the direction of the 

 opposite sex . . . the development and differentiation of one 

 sex is stimulated by the secretion of the gonads of the same 



