THE GENITAL GLANDS — UNION WITH MESONEPHROS 225 



at the fifth or sixth month it reaches a maximal diameter of 15 to 30 mm. At birth it is still 

 a prominent structure in the ovary and it is believed to produce an internal secretion; for if 

 the corpus luteum is removed the ovum fails to attach itself to the wall of the uterus. 



The Rete Ovarii. — The cells of the rete ovarii remain compact, distinct and 

 continuous only with the stroma of the medulla, the medullary cords. The anlage 

 is differentiated into a network of solid cords in 60 mm. embryos (head-foot 

 length) and these connect with the collecting tubules of the mesonephros. Some 

 time before birth lurnina appear in the cords transforming them into tubules 

 homologous with those of the rete testis. 



Anomalies. — The ovaries vary greatly in form and position. Congenital 

 absence of one or both glands is rare. Cases of supernumerary and bilobed ovar- 

 ies have been observed. 



Comparing the testis and ovary in development, it is clear that the superficial 

 epithelium after forming the inner epithelial mass takes no further part in the dif- 

 ferentiation of the testis and only a small part in that of the ovary. The testis 

 cords, rete testis and tunica albuginea are formed early from the inner epithelial 

 mass, which determines their form. The inner epithelial mass of the ovary de- 

 velops slowly and its passive cells are separated and surrounded by actively 

 ingrowing connective tissue. The primordial follicles when developed are not the 

 homologues of the testis cords and the tunica albuginea appears late. The rete 

 ovarii is the homologue of the rete testis but remains a rudimentary structure. 



The Union of the Genital Glands and Mesonephric Tubules. — In both male 

 and female embryos of 21 mm. the mesonephros has degenerated until, according 

 to Felix, only twenty-six tubules persist separated into a cranial and a caudal 

 group. In the cranial group of 5 to 12 tubules the collecting portions have sepa- 

 rated from the secretory portions. The free ends of these collecting tubules 

 project against that part of the inner epithelial mass which gives rise to the rete 

 tubules of either testis or ovary (Fig. 220). The cords of the rete develop in 

 contact with the collecting tubules of the mesonephros and unite with them. In 

 the male this union was observed by Felix in embryos of 60 mm. head-foot length. 

 The lumina of rete and coUecting tubules become continuous and the latter are 

 transformed into the ductuli ejferentes of the epididymis. They convey the sperms 

 from the testis tubules into the mesonephric duct, which thus becomes the male 

 genital duct. During the fifth month of pregnancy the ductuli efferentes coil at 

 their proximal ends and when surrounded by connective tissue they are known as 

 coni vasculosi. The cranial portion of the male genital duct also coils and forms 

 the canalis epididymis. Its blind cranial end persists as the appendix epididymis. 

 is 



