EENAL AND REPRODUCTIVE SYSTEMS 241 



front of the liver, to open into the abdominal cavity 

 by a median ventral slit, through which the ova enter 

 the oviducts from the abdominal cavity. 



About a third of its length from the anterior end, , 



each oviduct expands to form the thick-walled ovi- 



ducal gland, which secretes the horny capsules of 



the eggs. Behind the glands the oviducts are large 



and dilatable, with longitudinally folded walls : their 



posterior ends unite, and open by a large median 



aperture into the dorsal wall of the shallow cloaca, 



immediately behind the rectum. This aperture is 



closed in the young female, before fertilisation and 



oviposition have occurred, by a thin membrane, the 



hymen. 



Find the anterior opening of the oviducts in the suspensory 



ligament of the liver, immediately behind the perica/rdial 



wall : insert a seeker through it into the oviducts, and follow 



one of these back to the cloaca, slitting open its ventral wall. 



8. The kidneys extend nearly the whole length of the ab- 

 dominal cavity, lying dorsal to the peritoneum, and 

 one at each side of the vertebral column. The an- 

 terior half or more of each kidney, the mesonephros, 

 is rudimentary, and appears as an ill-defined tract 

 of soft yellowish-brown degenerate gland-tissue, ar- 

 ranged in patches corresponding to the vertebrae. 



The metanephros, which forms the posterior third 

 or so of the kidney, is a well-developed, compact, 

 laterally compressed, and lobulated mass of a brown- 

 ish colour, extending back as far as the level of the 

 cloaca. 



Dissect off the peritoneum from the ventral surface of one 

 of the kidneys, so as to expose it along its whole length. At 

 the kinder end dissect the metanephros along its outer side 

 from the body-wall, so as to see its.full size. 



4. The mesonephric or Wolffian ducts are a pair of straight 

 narrow tubes lying on the ventral surface of the 

 kidneys along their whole length. Their posterior 



B 



