104 BENJAMIN H. WILLIER 



The s-permatic cord. The gonads of specimens 44 and H-37 

 lie in peritoneal sacs, which are situated between the skin and 

 the abdominal wall in the region of the groin. These peritoneal 

 sacs are diverticula from the body cavity into which the gonads 

 have descended (both the gonads and spermatic cords are retro- 

 peritoneal, • and not in the cavities of the peritoneal sacs; the 

 peritoneal sac is merely wrapped around the gonad). In case 

 44 the cavity of the bulbular portion of the sac, which encloses 

 the gonad, communicates with the rest of the coelom (body 

 cavity) by a narrow canal. Along this channel is a passage- 

 way for the vas deferens, spermatic nerves, and blood-vessels. 

 These three structures loosely bound together by connective 

 tissue from the spermatic cord, as in the normal testis. Although 

 the gonad of H-46 is not descended into a peritoneal sac, a more 

 or less typical spermatic cord extends from its anterior end. 

 Its vascular cord is well formed (7 mm. in diameter), and enters 

 the anterior end of the gonad. Running parallel with the vas- 

 cular cord and loosely bound to it by connective tissue is the vas 

 deferens. In figure 10 the vascular cord {vp) is shown as a 

 plexus of blood-vessels, which have thick fibromuscular walls of 

 both circular and longitudinal fibers. 



GENERAL DISCUSSION 



In the free-martin a gonad with a primary female determina- 

 tion may transform into a structure which is morphologically a 

 testis. The fundamental determining factor in such a trans- 

 formation is the primary action of the male sex hormones. The 

 sex hormones suppress the development of the ovarian cortex 

 and stimulate the development of the other embryonic rudi- 

 ments. That is to say, the sex hormones in no case cause the 

 development of any new structure, as the primordium of each 

 male structure developed in the free-martin gonad is present in 

 the ovary at the time of sex differentiation. Whether sex hor- 

 mones can stimulate the development of any new structure has 

 not been demonstrated. However, if a gonad with a primary 

 male determination were to transform into an ovary by the 

 action of female sex hormones, a new structure, the ovarian 



