82 BENJAMIN H. WILLIER 



to which is a variable number of concentrically arranged lamellae 

 of connective-tissue fibers. As a rule, the number of lamellae 

 increases as the medullary type of cord is transformed into that 

 of a seminiferous tubule type. The wall of a normal seminif- 

 erous tubule has a similar composition, with many lamellae. 



In order to understand the changes undergone by a medullary 

 cord of the free-martin gonad as it transforms into a seminifer- 

 ous tubule, it will be necessary to consider briefly the structure 



Fig. 6 Portion of a transverse section through the sex-cord region of the 

 free-martin gonad, 66. bv, blood-vessel containing corpuscles; i, interstitial 

 cells; s, sexual cord which resembles a seminiferous tubule (note arrangement 

 of the nuclei of the supporting epithelial syncytium, and strands of cytoplasm 

 extending centrally from the inner ends of the nuclei) ; ts, sexual cord which shows 

 a transitional stage between a medullary cord and a seminiferous tubule (note 

 arrangement of nuclei within syncytium); ct, connective tissue. X 380. 



of the medullary cords of the normal embryonic ovary, and also 

 to follow the development of the syncytium of supporting epi- 

 thelial cells in normal embryonic testes and in three post-natal 

 testes. 



Examination of an ovary of a normal 8.3-cm. embryo (N 7), 

 shows that the medullary cords consist of solid strands of sup- 

 porting epithelial cells enclosed within definite walls. The 

 cells are closely crowded and irregularly arranged, and owing to 

 the absence of cell walls they form a syncytium. In a medul- 

 lary cord of an ovary from an 18-cml embryo there is some 



