THE STRUCTURE OF FREE-MARTIN GONADS 69 



the arrangement of the dots in the stippled area (sc). Entering 

 the anterior end of the gonad just below the rete is a distinct cord 

 of convoluted blood-vessels, which, aside from its eccentric 

 position, resembles the vascular cord (bv) of the normal testis (E). 

 The highest step in the transformation series is shown in dia- 

 gram D, which very closely resembles the normal testis (E). 

 By the growth of the sex-cord region, the rete (r) has been shifted 

 toward the center of the gonad, so that on all sides the rete 

 tubules make connections (st) with the sexual cords (sc). Al- 

 though the rete (?^) in D is still slightly eccentric in the sex-cord 

 region (sc), its position marks a distinct advance toward male- 

 ness; the rete normally forms a core in the center of the testis 

 (E) . At the anterior end of gonad D, the rete tubules (r) make 

 connections with the tubules of the head of the epididymis (he). 

 Attached to the posterior end of the gonad is the tail of the 

 epididjrmis (te), connected with the head (he) by the body of 

 that organ (be) . Passing anteriorly from the tail of the epididy- 

 mis (te) is a vas deferens (vd). It will be noted that as the 

 rete shifts toward the center of the gonad, the vascular cord 

 (hv) also moves in the same du-ection. In this highly trans- 

 formed gonad (D) the epididymal structures, vas deferens, and 

 rete are in essentially the same mutual relations as in the normal 

 testis (E). 



THE MICROSCOPICAL ANATOMY OF THE POST-NATAL GONADS 



The following pages comprise detailed descriptions of the 

 microscopical anatomy of the reproductive glands of nine post- 

 natal free-martins, comparisons with the structure of the gonads 

 of foetal free-martins and of normal gonads, and discussions 

 based on these comparisons. An examination of the microscop- 

 ical anatomy indicates considerable variation in structure. Some 

 have approximately the typical structure of a testis, while others 

 are much less typically male. In other words, they exhibit a 

 graded series of transformations between an ovary and a testis. 

 Three more or less distinct steps may "be recognized, which may 

 be characterized as low, medium, and high degrees of transfor- 

 mations in the male direction. An examination of this series 



