THE ORGANS OF THE MIDDLE GERM-LAYER. 409 



only inconspicuous remnants of it are left at its ends (hydatid of 

 the epididymis and sinus prostaticus or uterus masculinus) j in the 

 female it becomes the efferent apparatus of the ovary, the anterior 

 part the oviduct, the posterior part the uterus and vagina, the latter 

 resulting from the fusion of the ducts of the opposite sides of the 

 body as far as they are enclosed in the genital cord. 



31. In the male the anterior portion of the primitive kidney 

 (mesonephros) having united with the seminal tubules by means 

 of the sexual cords persists as the epididymis ; the remainder de- 

 generates into the paradidymis. In the female both parts degenerate 

 into epobphoron and paroophoron, which correspond respectively to 

 the epididymis and paradidymis of the male. 



32. The sexual glands, which are originally established in the 

 lumbar region, gradually move with their outlets downward toward 

 the pelvic cavity. (Descensus testiculorum et ovariorum. Oblique 

 course of the spermatic arteries and veins.) 



33. In the migration of the sexual glands a role appears to be 

 played by the inguinal ligament, which passes from the primitive 

 kidney underneath the peritoneum to the inguinal region, penetrates 

 through the wall of the abdomen, and ends in the skin of the genital 

 ridges that surround the cloaca. (Gubernaculum Hunteri in the 

 male ; round ligament and ligamentum ovarii of the female.) 



34. The testis is received some time before birth into the scrotum, 

 an appendage of the body-cavity ; the scrotum owes its origin to the 

 fact that the peritoneum forms an evagination (processus vaginalis 

 peritonei) through the wall of the abdomen into the genital ridges, 

 and that afterwards the evagination is completely cut off from the 

 body-cavity by the closure of the inguinal canal. 



35. The layers of the scrotum or the envelopes of the testes corre- 

 spond, in accordance with their development, to the separate layers of 

 the body- wall, as is shown in the following comparative summary : 



Envelopes of the Testes. Wall of the Abdomen. 



Scrotum with tunica dartos. Skin of the abdomen. 



COOPER'S fascia. Superficial abdominal fascia. 

 Tunica vaginalis communis with . Muscle-layer and fascia trans- 



cremaster. versa abdominis. 



Tunica vaginalis propria (parietal Peritoneum. 



and visceral layers). 



36. The external sexual organs are developed in man and woman 

 from the same kinds of fundaments in the neighborhood of the cloaca. 



