THE STRUCTURE OF FREE-MARTIN GONADS 85 



parallel to each other and perpendicular to the tube wall. From 

 the inner end of each nucleus extends a strand of cytoplasm 

 toward the center of the tubule; the point where these strands 

 center has the potentiahty of forming a lumen. Within this 

 syncytium are found a few large, clear cells — the primordial 

 germ cells. 



Bearing in mind the history of the medullary cords and the 

 normal development of the seminiferous tubules, the develop- 

 ment of the seminiferous tubule in the free-martin is compre- 

 hensible. The medullary type of sexual cord resembles not 

 only the medullary cords of the normal ovary, but also the 

 youngest sexual cords in the testis, these being homologous 

 structures. As a sexual cord in the free-martin, originally of 

 medullary type, transforms into a seminiferous tubule, it passes 

 through stages which are in essentials similar to those in the 

 .normal development of the seminiferous tubule. 



The sex-cord region of H-42. The sex-cord region of this 

 gonad presents a striking contrast to the sex-cord region of other 

 gonads of the entire series, in showing a few female elements. 

 This region is smaller and much more poorly organized than in 

 the other cases of this group of moderately transformed gonads. 

 It is made up chiefly of masses of interstitial tissue (connective- 

 tissue stroma and interstitial cells) , in which are scattered sexual 

 cords. Of the two types of sexual cords, the larger number here 

 resemble seminiferous tubules, while a few are distinctly female, 

 possessing primary follicles containing germ cells. These sexual 

 cords which resemble seminiferous tubules show different degrees 

 of organization of the syncytium of supporting epithelial cells; 

 in some the nuclei are arranged in a single layer and in others 

 they are irregularly arranged and closely packed. The walls of 

 these sexual cords are thickened, otherwise they agree very closely 

 in structure with the sexual cords of cases 66, 42, and H-18 

 described above, and therefore will not be considered -further. 



The sexual cords which appear to be female in structure are 

 located largely near the periphery of the sex-cord region. They 

 are composed of a typical egg cell surrounded by a single layer 

 of more or less flattened follicular epithelial cells. In some more 



