36 TADACHIKA MINOURA 



know what sex the embryo would have been if allowed to develop 

 without experimental interference. Nevertheless, examination 

 of these embryos permits us to draw with reasonable certainty 

 some conclusions concerning their original sex and the degree 

 to which this sex had been modified in the direction of the 

 opposite sex. 



It is highly probable that certain of these embryos which 

 received testis grafts were originally females and were subse- 

 quently modified in the male direction through the presence of 

 the testis graft. This appears to be the case in embryos nos. 

 27-6, 31-3, 47-10, 43-3, 27-5. Certain structural features of 

 these embryos indicate that they had originally developed and 

 differentiated to a certain extent in the direction of femaleness. 

 This is evidenced principally by the presence and degree of 

 differentiation of the miillerian ducts; both conditions are similar 

 to those of the female. It is difficult — in fact, impossible — to 

 account for the condition of the miillerian ducts in these embryos 

 except on the basis that the embryos were originally females and 

 had differentiated to this extent in the female direction. There 

 is no possibility that the presence of testis grafts on such embryos 

 could have induced the differentiation of the miillerian ducts. 

 Hence we are compelled to believe that these embryos were 

 originally females. But they possess gonads of the male type. 

 There is no escape from the conclusion that their gonads, origi- 

 nally ovaries, have been greatly modified in the male direction 

 through the action of the secretion from the testes grafted on 

 their membranes. 



Certain other embryos of the female type show modification 

 in the male direction, as embryos nos. 17-7, 22-13, 22-9. In 

 these cases the embryos were eleven and thirteen days old when 

 the testis graft was implanted on them. They had therefore 

 attained considerable differentiation in the female direction 

 before the testis hormone acted upon them. In these cases the 

 right ovary persisted — a result which must be ascribed to the 

 action of the testis hormone. We may say that the testis secre- 

 tion cannot cause the disappearance of the right ovary, or, to 

 put the matter in another way, it tends to make both gonads 

 develop equally. 



