142 



SUB-CLASS ELASMi >BRANCHII. 



cula seminalis (Fig. 81, vs). The two vesiculse seminales join 

 to form the urogenital sinus and just before their union each 

 receives the opening of the seminal bladder (ss), which is a 

 pouch lying on the ventral side of the vesicula seminalis, and 

 the openings of the ureters, usually four or five in number in 

 Scyllium canicula. The urinary sinus which in the male is 

 common to the urinary and generative organs opens into the 

 cloaca through its dorsal wall by a median papilla the urino- 

 genital papilla (ug.p.). 



In the female the hind end of the longitudinal duct is dilated 

 (ub) and receives not far from its union with its fellow the ureters 



(ur) by one or 



5 more openings. 



The oviducts 

 open close to- 

 gether through 

 the dorsal wall 

 of the cloaca 

 in front of the 

 urinary papilla. 

 They extend for- 

 ward to the front 

 end of the body 

 ca v ity into 

 which they open 

 close together 

 on the ventral 

 side of the 

 anterior end of the liver (fl.tf). Not far from their front end their 

 walls are much thickened owing to the presence of glandular 

 tissue constituting the oviducal gland (od.g). 



Traces of the oviducts are often present in the male, particu- 

 larly near the abdominal openings. 



The oviduct in the viviparous forms presents a uterine dilata- 

 tion and the oviducal gland is much reduced. 



In many Selachii the nephrostomes of a certain number of 

 the primary kidney tubules persist into the adult as ciliated 

 openings. These are minute in Scyllium, but in some forms they 

 attain a considerable size. 



The egg is large and heavily yolked. It receives a coat of 



FlQ. 80. Testis and anterior part of niesonephros (Wolffian 

 body) of an embryo of Squatina vulgaris (after Balfour) : to 

 show the testicular network. There are five vasa efferentia 

 connecting the longitudinal canal in the base of the testis 

 with a longitudinal canal in the mesonephros. From the 

 latter there pass off four ducts to as many malpighian bodies. 

 1 vasa efferentia ; 2 malpighian bodies ; 3 mesonephros ; 

 4 longitudinal or mesonephric duct ; 5 longitudinal canal of 

 the testis ; 6 testis. 



