170 Sex-Reversal in Frogs and Toads 



season in cases thus operated upon, but they certainly do not atrophy. 

 In the cases in the lists, it is seen that only in those in which there 

 still remained some ovarian tissue capable of producing ova, though 

 they were abnormal and degenerate, did the oviducts exhibit a seasonal 

 increase in size and activity. In the majority their glandular portions 

 still retained the power of manufacturing their particular secretion, -for 

 in water the ducts became much swollen, and this is a further proof that 

 the ducts do not undergo any considerable degree of atrophy. 



There is no evidence that the seasonal activity of the testis in these 

 cases produces a corresponding increase in the size and activity of the 

 Mtillerian ducts, as would be expected from the results of the experi- 

 ments of Harms and Meisenheimer. It is seen, as has been stated above, 

 that this increase is only shown in those cases in which ovarian as well 

 as spermatic tissue was present in the gonads. 



It seems probable, therefore, that when the gonad has the constitu- 

 tion represented by the formula Ov. 1, oviducts become developed up 

 to the female standard ; that when the gonad's composition becomes 

 that represented by Sp. 1, Ov. 1, vasa efferentia and seminal vesicles 

 make their appearance ; and that coincidently with the fuller develop- 

 ment of the testis-portion of the ovo-testis, the male accessory repro- 

 ductory apparatus attains the form and size of that of the typical male, 

 while the oviducts, having reached a considerable size already, retain 

 their form throughout the process which is converting a young female 

 into a somatic male. 



Granting that the hormones of the gonad are responsible for the 

 stimulus which calls forth the development of the accessory reproductive 

 apparatus, it is seen that the exhibition of the specific male hormones 

 does not cause the development of any structure which is not repre- 

 sented embryologically in the normal female, and that hormones act 

 merely by inhibition or stimulation of normal embryonic rudiments. 



The Miillerian ducts were of unequal development in a few cases, 

 and in these the better developed duct was on the side of the body on 

 which more ovarian tissue was still present (cf. Aves). 



