EFFECTS OF GONAD GRAFTS IN CHICKS 37 



In the case of ovary grafts, certain embryos were obtained 

 which were probably originally males and which have been modi- 

 fied in the female direction. Such cases are nos. 27-4 and 2-5. 

 These embryos have gonads of the male type, but the left gonad 

 is considerably larger than the right one. We may conclude 

 that these gonads began to develop in the male direction, but 

 after coming under the influence of the ovary graft developed 

 in the female direction. The miillerian ducts of these embryos 

 also show a modification in the female direction; the left duct 

 is better developed and more differentiated than the right one. 

 The left duct does not, moreover, show any signs of degeneration. 

 These conditions can again be interpreted as the consequence 

 of the action of an ovarian secretion upon an originally male 

 embryo. Similar conditions are exhibited by embryos nos. 

 17-1, 17-5, and 18-9, which also received ovary grafts. These 

 embryos have gonads of the male type, but the left one is again 

 larger than the right one and there are no miillerian ducts. These 

 embryos may be regarded as originally male embryos which were 

 less markedly modified in the female direction than is the case 

 with the two embryos just discussed, nos. 27-4, and 2-5. The 

 reason for this becomes apparent when the experimental con- 

 ditions in these cases are considered. Grafts were made on 

 embryos nos. 17-1, 17-5, and 18-9 when they were eleven and 

 thirteen days old. Hence they had already undergone con- 

 siderable differentiation in the male direction, and it is not to 

 be expected that the ovarian secretion could produce such 

 marked effects at that late stage of development as in the cases 

 of nos. 27-4 and 2-5, where the grafts were implanted at nine 

 and seven days, respectively. 



Female-type embryos nos. 30-6, 29-5, 1-7, 17-4, 30-9, and 

 44-16, on which ovary had been grafted, are somewhat puzzling. 

 These embryos have a persistent right gonad. It is difficult 

 to say whether these embryos were originally male and have been 

 markedly transformed in the female direction or whether they 

 were originally females in which the gonads have been stimulated 

 to supernormal development by an excess of ovarian secretion. 



