COMPARATIVE ANATOMY 67 



the two sides open into the urinary sinus, which lies in the 

 urinary papilla in the cloaca. The Wolffian duct is difficult to 

 locate in females. It lies on the ventral side of the anterior 

 part of the kidney; in immature females it is directly beneath 

 the oviduct, and in mature adults along the attachment of the 

 mesentery supporting the oviduct. It empties with the Wolffian 

 duct into the urinary sinus of the urinary papilla. 



Urogenital Organs of the Male Necturus 



The testes are elongated and He dorsal to the small intestine. 

 Each is supported by a mesentery, the mesorchium. The kid- 

 neys or mesonephroi lie dorsal and posterior to the testes. The 

 anterior end may not be excretory in function. The Wolffian 

 or mesonephric ducts, much coiled, lie along the lateral borders of 

 the kidneys and serve for the passage of both the sperm and the 

 excretions of the kidneys. The vasa efferentia, tubes which 

 carry sperm from the testis to the kidney, may be seen as white 

 ducts in the mesorchium. The sperm pass from the vasa 

 efferentia through the tubules of the kidney to reach the Wolf- 

 fian duct. Trace the Wolffian ducts to the cloaca. 



Slit open the cloaca and try to find the entrances of the 

 Wolffian ducts. Find also the entrance of the large intestine 

 and of the urinary bladder. How does urine get into the bladder ? 



Urogenital Organs of the Female Necturus 



The ovaries are sac-like structures containing the eggs. 

 Each is supported by a mesentery, the mesovarium. The large 

 white coiled tubes running the length of the body cavity, lateral 

 to the ovaries, are the oviducts. Trace the oviduct forward and 

 find the thin-walled expanded end, with an opening, the ostium, 

 leading into it. Posteriorly the oviducts join the cloaca. 



The kidneys or mesonephroi lie dorsal to the ovaries and 

 median to the oviducts. The Wolffian or mesonephric ducts, 

 much smaller here than in the male, lie along the lateral borders 

 of the kidneys. To see where the mesonephric ducts and the 

 oviducts enter the cloaca, free the cloaca from the body wall. 

 Observe also the entrance of the urinary bladder and of the 

 intestine into the cloaca. 



