XI 



UROGENITAL SYSTEM 



UROGENITAL SYSTEM OP HEPTANCHUS MACULATUS 



Urinary System 



The mesonephrotic kidneys in Heptanchus (kd., fig. 251) appear as right and 

 left longitudinal bands lying along the entire roof of the body cavity and at 

 the sides of the spinal column. Each kidney extends as a narrow ribbon of 

 tissue from the pericardio-peritoneal septum posteriorly one-half the length 

 of the body cavity; back of this it broadens out and becomes much thicker so 

 that the main mass of the tissue lies posterior to the region of the superior 

 mesenteric artery. 



In general it may be said that the kidney is made up of multitudes of small 

 lobules which in ventral view give little evidence of segmentation. A close 

 study, however, reveals the fact that a division into segments is present. This 

 may be further verified by the segmental arrangement of the collecting tubules 

 which extend from the kidney tissue to the Wolffian duct (iv.d.), or in the 

 posterior part to the ureter (u.). 



From the upper part of the kidney the collecting tubules enter the Wolffian 

 duct and in the lower part they join the enlarged ureter. In an immature fe- 

 male ten of these collecting tubules may be seen to join the Wolffian duct on its 

 median side and twelve to join the ureter laterally, twenty-two in all being 

 present. A similar condition is present for the upper part of the kidney of the 

 adult female as is seen in figure 252 (facing p. 290) . But in that figure the ure- 

 ter has not been thro\\ai to the side and so not all the ducts entering it appear. 



In the immature female (fig. 251a, 70.3 em. in length) the Wolffian duct 

 passes the entire length of the kidney apparently as a straight tube, increas- 

 ing from 0.5 to 1 mm. in size. In its anterior segment it lies just ventral to the 

 kidney, and in the posterior division it passes along the ventral and median 

 margin of the ureter. In the lower part of its course it does not receive col- 

 lecting tubules. 



The Wolffian duct of the adult female (fig. 252) presents a most interesting 

 condition in its upper segment where it is singularly coiled like that of the 

 male. This distinct torsion, however, extends only a little over one-half of the 

 anterior segment or to the posterior part of the sex gland (ov.). The remain- 

 ing part of this segment is straight and the posterior segment, like that in the 

 immature female, passes ventral to the enlarged ureter. 



The ureter in Heptanchus is a thin walled, elongated blind sac which in the 

 immature specimen above described reaches a diameter of 7 mm. Anteriorly, 

 and essentially at the segment where the kidney begins to increase in size, the 



[287] 



