1 64 Sex-Reversal in Frogs and Toads 



When the abnormalities of the reproductive system are thus arranged 

 in a graduated series, they appear to be merely phases of one process at 

 the beginning of which the gonad has the appearance of a normal typi- 

 cal ovary, and at the end of which the same gonad is in every way a 

 typical testis. At the beginning, the gonad is an ovary of considerable 

 size, and is capable of functioning as such and of producing mature ova 

 (Case 1 Rt) ; it contains many ova in various stages of development, 

 and a considerable amount of undifferentiated germ-tissue, much of 

 which is situated upon the inner border of the gonad. Then upon this 

 inner border, one or several patches of spermatic tissue make their 

 appearance (Cases 3 and 4 Lt). These have developed from the hitherto 

 undifferentiated germinal tissue of this region. Very soon after this, 

 the ovarian tissue of both gonads begins to show signs of degenera- 

 tive changes, such as an increase in the relative amount of pigment, a 

 diminution in the size of the nuclei of the ova, and a shrinking of the 

 cytoplasm with vacuolaticm (Case 2). The spermatic tissue progres- 

 sively increases in amount, and the ovarian undergoes progressive 

 degeneration, becoming less and less in amount, and more and more solid 

 in consistence, while the pigmentation becomes more and more, intense. 

 Fewer and fewer ova are found within its shrinking bulk (Cases 4 Lt, 

 5 Rt), until at length the gonad assumes the form of a testis irregular in 

 shape, and with its surface scarred with deep grooves, which bears 

 upon its outer border a sub-peritoneal crest of jet-black nodules of pig- 

 ment cells and fibrous tissue (Case 14 Rt). This pigment, now a harmful 

 foreign body, is slowly removed by the blood-stream, and can be identi- 

 fied within the renal veins, and the testis, becoming healed, ultimately 

 assumes the form and appearance of the normal gonad of the typical 

 male (Cases 25-32). 



It seems clear that at the beginning one gonad — usually the right 

 — is the seat of this transformation, for when both gonads are affected, 

 they exhibit two different phases of the process, that in one being more 

 advanced than that in the other, and it seems that the occurrence of 

 this phenomenon in one gonad favours its onset in the other. Since the 

 degeneration of the ovarian tissue is often equally pronounced in the 

 ovary of the opposite side, it is reasonable to assume that in every case 

 in the lists, both gonads have been, are, or would have been affected. 



Ova are often found amid the spermatic tissues of the testis-portion 

 of an ovo-testis and of an otherwise normal testis. Normally ova are 

 extruded from the surface of an ovary. In an ovo-testis they are 

 extruded from the ovarian portion into the testis-portion (or the actively 



