REPTILIA 571 



The renal portal system drains a considerable portion of the body. 

 The venous blood from the tail is carried by means of a caudal vein. 

 It lies ventrally to the caudal vertebrae, and bifurcates at the base 

 of the tail to form the two lateral pelvic veins. Each of these passes 

 across the ventral face of the corresponding kidney to contact the 

 posterior edge of the corpora adiposa. Each receives efferent veins 

 from these bodies, at the anterior border of which the pelvic veins 

 empty into the epigastric or anterior abdominal vein. This vein ex- 

 tends anteriorly along the inner face of the body wall to enter the 

 left lobe of the liver on the posterior face. The renal portal veins 

 receive the pelvic veins near the kidneys. The pelvic veins are formed 

 by the union of the femoral and the sciatic veins from each hindlimb. 



The right precava is located in the lateral neck region and passes 

 posteriorly to the sinus venosus. It is formed by the union of the 

 internal and external jugulars. For a short distance it is the common 

 jugular. Then it receives the right subclavian vein which returns 

 the blood from the right forelimb. From that point on it is the right 

 precava. The left precava is formed by the union of the left internal 

 jugular and the left subclavian veins. The left external jugular is 

 not present. The right and left precavae converge with the postcava 

 and enter the sinus venosus. 



The Urinogenital System 



The reptilian urinogenital system shows decided advances over 

 the types of urinogenital systems found in lower vertebrates. The 

 mesonephric type of kidney found in lower groups is replaced by 

 a metanephric type of kidney in the reptiles. The products of the 

 gonads are conducted through special ducts from these glands and 

 not through the kidney, as in lower animals. Instead of producing 

 hundreds of small eggs in a season, as in certain amphibians and 

 fishes, the horned lizard lays twenty to twenty-five eggs of moder- 

 ate size. The eggs of all vertebrate classes below reptiles are with- 

 out shells. This makes external fertilization possible and necessi- 

 tates an aquatic nesting site. The eggs of reptiles are covered by 

 a tough, thick shell. Fertilization must occur internally before the 

 shell is put on; hence, the males have intromittent copulatory or- 

 gans for introducing spermatic fluid into the females. Such eggs 

 will develop on land and often in rather dry places. The oviducts 



