108 BENJAMIN H. WILLIER 



A question of considerable importance to the problem of sex- 

 differentiation in mammals is to determine the limit of trans- 

 formation of an ovary in the male direction by the action of sex 

 hormones. The most extreme case is the gonad of H-37. 

 Although the gonad (left) has attained a comparatively large 

 size, it is nearly twenty times smaller than a normal testis of 

 approximately the same age. Structurally, it is a typical testis 

 in every respect except that all stages of the male germ cells are 

 absent. So complete is the transformation that some doubt 

 may arise as to its classification as a free-martin gonad. How- 

 ever, the following facts indicate without a reasonable doubt 

 that the gonads are from a free-martin: 1) The specimen in 

 question was born co-twin to a normal bull. 2) The external 

 genitalia are predominately female, although the clitoris is 

 partially transformed into a perforated penis. Numan ('43) 

 figures in his plate XI (refigured by Lilhe, '17, fig. 29) the repro- 

 ductive system of a free-martin, which shows the external 

 genitalia transformed in a manner almost identical with that of 

 case H-37. 3) The gonad of this specimen forms a member of a 

 graded series of transformations in the male direction. 4) The 

 internal reproductive system, aside from. the gonads, is in all 

 essentials of the usual free-martin type, except there is a greater 

 progression in the male direction. 5) The possibility that the 

 gonads are from a cryptorchid male is dismissed by the fact that 

 in all cryptorchids the external genitalia are normal. Further- 

 more, cryptorchidism in cattle has not been reported. Obvi- 

 ously, then, an ovary under the influence of male sex hormones 

 may transform into a testis which is morphologically complete, 

 but which is functionally inactive so far as the production of 

 germ cells is concerned (the interstitial cells may be physiologi- 

 cally active). 



Such a reproductive gland approaches very closely, if not 

 actually reaches the limit of transformation in the male direction 

 by hormonic action, a condition which indicates that the opti- 

 mum conditions for the transformation of an ovary were fairly 

 closely realized in this case. What are the optimum conditions? 

 The optimum conditions, so far as the primary cause is con- 



