64 BENJAMIN H. WILLIER 



develop, while the distmctly female structures, the cords of 

 Pfliiger, and definitive ovarian albuginea fail to develop. 



In both the foetal and post-natal gonads of free-martins, the 

 tunica albuginea, sex-cord region, and rete are of constant 

 occurrence, although each structure may vary greatly as to size, 

 degree of differentiation, and degree of transformation in the 

 male direction. Such structures as the tubules of the epididymis 

 and the spermatic cord are in some specimens entirely absent. 

 There may be a correlation between this high degree of variation 

 in the structure of the reproductive glands of the free-martin 

 and the time and degree of anastomosis ' of the blood-vessels of 

 the two blastodermic vesicles. In other words, there may be 

 considerable variability in the tune at which the internal secre- 

 tion enters the circulation of the female twin; variations in 

 quantity of the hormone and in the intensity of its action are 

 also conceivable. 



Owing to these male characteristics of the gonad, several 

 investigators have misinterpreted the true sex of the free-martin. 

 Hart ('10) and Magnusson ('18), who described the microscopical 

 anatomy of the reproductive organs of the post-natal free-martin, 

 both reached the conclusion that it is an abnormal male. It 

 was not until the embryological history of these gonads was 

 known that a correct interpretation was possible. With the 

 embryological data and from an examination of a number of 

 post-natal gonads of the free-martin, the conclusion is reached 



tional seminiferous tubules, while in the case of the ovary there are two sets of 

 sexual cords; the first set forms the medullary cords, which are destined to degen- 

 erate and which are homologous with the seminiferous tubules; the second set 

 forms the cords of Pfliiger. 



The term sex-cord region is used to include both the sexual cords and the inter- 

 cordal tissue (stroma of connective-tissue fibers between which are the inter- 

 stitial cells). 



The term rete is applied to the network of tubules of the rete testis, of the 

 rete ovarii, and of the modified rete of the free-martin gonad. 



The term tunica albuginea is used to designate the connective-tissue capsule 

 of the testis, and the layer of connective tissue between the medullary cords and 

 the cords of Pfliiger of the ovary. It is the primary tunica albuginea of the 

 ovary and the definitive tunica albuginea of the testis. In the ovary a second 

 layer of connective-tissue fibers develops between the cords of Pfliiger and the 

 germinal epithelium; this is the definitive tunica albuginea of the ovary. 



