264 THE DOG-FISH. 



along the dorsal wall of the abdominal cavity 

 ventral to the kidneys, and nob 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 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 

 oviducal 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 wall : 

 insert a seeker through it into the oviducts, and follow one of 

 these back to the cloaca, slitting through its ventral wall. 



3. The kidneys, or mesonephra, extend nearly the whole 

 length of the abdominal cavity, lying dorsal to the 

 peritoneum, and one at each side of the vertebral 

 column. The anterior half or more of each kidney 



Fig. 55. Scyllium canicula. Dissection of a female from the ventral 

 surface, to show th8 renal and reproductive systems. The right 

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

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

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



Fig. 56. 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, c, cloaca. E. 

 oesophagus, f, pelvic fin. G, gill-slit. |_, liver, o, ovary. OD, oviduct. 

 OD', oviduct laid open. OG, oviducal gland. OV, egg in the oviduct, p, 

 abdominal opening of oviduct. PG, pelvic girdle. R, rectum. RO, opening 

 of reatum into cloaca. S, anterior part of kidney. SD, Wolffian duct. 

 T, hinder part of kidney. TD, posterior ducts or ureters. TO, openings 

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

 ventricle. 



