RENAL AND EEPRODUCTIVE SYSTEMS. 261 



which runs straight hack along the ventral surface 

 of the metanephros to open into the urino- genital 

 sinus, just in front of the cloaca. The walls of the 

 vesicula seminalis are marked by close-set transverse 

 lines, corresponding to internal foldings of its lining 

 membrane. 



The Wolffian duet acts as vas deferens, conveying 

 the spermatic fluid from the testis to the exterior, 

 besides acting as the excretory duct for the meso- 

 nephros. 



Dissect the Wolffian duct of one side away from the ventral 

 surface of the mesonephros, notijig the tubules it receives from 

 this ; and follow it back to the cloaca. 



5. The sperm- sacs are a pair of thin-walled tubes lying along 

 the ventral surfaces and the outer sides of the vesiculee 

 seminales, to which they are closely attached, and 

 which they about equal in length. Each sperm-sac 

 ends blindly in front, and dilates behind to form the 

 urino-genital sinus. 



Dissect away the sperm-sac from the vesicula seminalis 

 and follow it bach to the urino-genital sinus. 



Fig. 55. — Scyllium oanioula. Dissection of a male from the ventral 

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

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

 the rectum have been removed. The excretory organs of the left 

 side only are shown. An arrow passes through the left abdominal 

 pore into the abdominal cavity, (a. m. m.) 



Fig. 56. — Further dissection of the renal and reproductive organs. 

 The liver and the greater part of the testis have been removed. 

 The right metanephric duct is shown in its natural po.sition ; the 

 left duct hjiS been displaced outwards. The urino-genital sinuses of 

 both sides have been laid open. (a. m. m.) 



AP, abdominal pore. CP, clasper. CR, groove in clasper. CS, sac con- 

 tinuous with groove in clasper. B, cesophagus. I", pelvic fin. G, gill-slit. 

 H, testis. L, liver. P, abdominal opening of MuUerian ducts. PD, abor-, 

 tive MUlIerian duct. PG, pelvic girdle. E, rectum. EG-, rectal gland. EO, 

 opening of rectum into cloacti, S, WolfHan body or mesonephros. SD, 

 WolflBau duct or vas deferens. SO, opening of WolfiBan duct into urino-genital 

 sinUs. SS, sperm-sac. T, metanephros. TD, metanephric duct or ureter. 

 TD', ducts from hinder part of metanephros, joining the ureter as it reaches 

 the lurino-genital sinus. TO, opening of ureter into urino-genital sinus. TIP, 

 urino-genital papilla, US, urino-genital sinus. VE, vasa effei«ntia. VS. 

 vesicula seminalis, the dilated hinder end of the WolfiBan duct. 



