464 CATHARINE LINES CHAPIN 



On a level with the anterior end of the gonad there is a portion 

 of the Miillerian duct, 0.080 mm in length, surrounded by the 

 connective tissue structure which normally encloses it (cf. 

 f-m. 13, page 474). The Wolffian duct begins anterior to the 

 gonad. At intervals, other ducts enter it from the Wolffian 

 body. It is irregular, in some places large and clearly defined, 

 with a wide lumen, at other points small with the lumen indistinct. 

 Summary. The gonad of the 12.5 cm. free-martin resembles a 

 testis in the appearance of albuginea and peritoneum, and in the 

 ^act that only one set of sex cords is present. In the position 

 of the rete, it resembles an ovary. The Wolffian duct is incom- 

 plete as in the female and the Miillerian duct is degenerating, as 

 in the male. 



3. FREE-MARTIN, 16.3 CM. T6 



(See fig. 16, Lillie.) Both the free-martin and the normal 

 male twin were studied. The free-martin measured 16.3 cm. 

 and the male measured 16.8 cm. The gonad and Wolffian body 

 were sectioned in both embryos; in the free-martin, the ducts 

 posterior to the Wolffian body were also sectioned. 



a. Normal conditions at this stage 



The male, as is usual in this type of twins, is normal. The 

 testis is 4.86 mm. long. The rete enters the gonad almost at its 

 extreme anterior end. The seminiferous tubules which radiate 

 from the rete are numerous and more branched than those of 

 younger males (cf. cf T16 or T25). They are separated from 

 each other by connective tissue and interstitial cells. Germ 

 cells in the seminiferous tubules are found in the indifferent 

 stage and early stages of the growth period. A wide, compact 

 albuginea is present. The anterior part of the Wolffian body 

 has become the epididymis, the tubules of which are more con- 

 torted than those of the epididymis in smaller males. Degen- 

 eration is going on throughout the rest of the Wolffian body. 

 The Wolffian duct is complete and, through part of its course, 

 lies in the fold of peritoneum overhanging the testis The 

 tubular part of the Miillerian duct has atrophied. (Posterior 

 part of ducts not sectioned.) 



