106 BENJAMIN H. WILLIER 



gonad are spermatozoa present. His figure 1, plate II, shows 

 seminiferous tubules, which in addition to the ordinary epi- 

 thelium (Sertoli cells) show a few rounded cells which resemble 

 in some respects primordial germ cells. No such picture of a 

 seminiferous tubule of a free-martin showing either primordial 

 germ cells or spermatozoa is shown in any of the specimens that 

 I have examined. Certainly, such an important exception 

 should have received more than brief mention. 



In some of the foetal free-martin gonads a small proportion of 

 the sexual cords enclose primordial germ cells, which, however, 

 are destined to degenerate before birth. That these germ cells 

 are distinctly female in character is shown by comparing them 

 with the primordial germ cells of the medullary cords of normal 

 foetal ovaries in cattle. As to origin, they are alike since the 

 sexual cords of the free-martin gonad are medullary cords which 

 are transforming into seminiferous tubules. The fate of the 

 primordial germ cells is the same in both the free-martin gonad 

 and the normal foetal ovary. The medullary cords with their 

 germ cells degenerate and disappear before birth in the normal 

 ovary of cattle, the first to disappear being the germ cells. Allen 

 ('04) has described a similar fate of the primordial germ cells 

 found in the medullary cords of rabbit and pig ovaries. It would 

 appear that this phenomenon is the regular event in the develop- 

 ment of the mammahan ovary. Since these primordial cells in 

 the sexual cords of the free-martin gonad and in the medullary 

 cords of the normal foetal ovary are identical as to origin, struc- 

 ture, degeneration changes, and disappearance before birth, it 

 seems reasonable to conclude that the primordial germ cells of 

 foetal free-martin gonads are female in type. 



As the sex-cord region shows more pronounced male organiza- 

 tion, the rete region simultaneously makes progress in the male 

 direction in several particulars. In the first place, its primitive 

 position at the hilus of the gonad is more or less lost by the 

 growth of the sex-cord region around its sides. However, the 

 growth of the sex-cord region is not sufficient even in the most 

 completely transformed gonads to bring the rete into the center 

 of a cylindrical gonad as it is in the normal testis (fig. 1, D and 



