256 THE DOG-FISH. 



along the dorsal wall of the abdominal cavity 

 ventral to the kidneys, and not far from the median 

 plane. Their anterior ends curve inwards round the 

 sides of the oesophagus, and unite immediately in 

 front of the liver, to open into the abdominal cavity 

 by a median ventral sht, 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 by a thin membrane, the 



hymen. 



Find the anterior opening of the oviducts in the suspensory 



ligament of the liver, immediately behind the pericardial 



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



one of these back to the cloaca, slitting through 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. 



Pig. 53. — Soyllium oaaiciila. Dissection of a female from the ventral 

 surface, to show the renal and reproductive systems. The right 

 lobe of the liver and the alimentary canal from the oesophagus to 

 the rectum have been removed. An arrovsr is passed up the left 

 oviduct, which is cut open to show its point, (a. m. m.) 



Fig. 54. — Further dissection of the renal and reproductive systems. 

 The left oviduct is removed ; and the right oviduct and the urinary 

 sinuses are laid open. (a. m. m.) 



A, auricle. AP, abdominal pore. B, pericardial cavity. O, cloaca. 

 E, oesophagus. F, pelvic fin. G, gill-slit. L, liver. O, ovary. OD, ovi- 

 duct. OD', oviduct laid open. OG, oviducal gland. OV, egg in llie 

 oviduct. P, abdominal opening of oviduct. PGr, pelvio girdle. R, rectum. 

 RO. opening of rectum into cloaca. S, Wolffian body or mesonephros. SD, 

 WoliEan duct. T, metanephros. TD, metanophric ducts or ureters. TO, 

 openings of ureters into urinary sinus. UP, urinary papilla. US, urinary 

 sinus. V, ventricle. 



