66 BENJAMIN H. WILLIER 



GENERAL INTERPRETATION OF THE POST-NATAL GONADS 



Diagrammatic reconstructions shown in figure 1 summarize 

 the detailed study presented beyond. The gonads of the free- 

 martin may be divided into three groups, characterized, respec- 

 tively, as low, medium, and high degrees of transformations in 

 the male direction. These three groups are represented in 

 figure 1 (B, C, and D) as graphic reconstructions and constitute 

 a chain of connected links between an embryonic ovary (A) and 

 a testis (E). For comparison similar graphic reconstructions of 

 ovaries (A' and A") and a testis (E) are introduced. Diagram 

 A represents an ovary in the indifferent stage of development. It 

 is covered with a superficial layer, the germinal epithelium 

 (ge), from which the first set of sexual cords (sc) arise by invag- 

 ination. At the anterior end, the rete tubules (r) enter the 

 hilum and project for a short distance posteriorly into the sex- 

 cord region (sc). The ovarian blood-vessels (bv) also enter the 

 gonad at the hilum. Under normal conditions, this gonad (A) 

 differentiates into an ovary, but under the influence of the male 

 sex hormones it differentiates into a gonad which is morphologi- 

 cally a testis. 



Diagrams A' and A" illustrate in two stages the normal differ- 

 entiation of an ovary from the indifferent stage A. The ovary 

 shown in A' may be regarded as derived from the indifferent 

 stage A by the addition of a second set of sexual cords, the cords 

 of Pfliiger (p), which arise as secondary prohferations of the 

 germinal epithelium (ge). Between the first set of sexual cords 

 (sc), which in the ovary are know-n as medullary cords, and the 

 cords of Pfliiger (p) is located the primary tunica albuginea (ta), 

 homologous with the tunica albuginea (ta) of the testis (E). 

 Between the germinal epithelium (ge) and the cords of Pfliiger 

 (p) is the deflnitive ovarian albuginea (oa), which has no homo- 

 logue in the testis. The rete tubules (r) have penetrated to the 

 posterior end of the medullary cord region, their eccentric posi- 

 tion is retained, and connections (tubuli recti) are never estab- 

 lished between the medullary cords (sc) and the rete tubules (r). 

 The arrangement of the dots in the stippled area (sc) of the 



