223 



mandibular muscle, and goes forward to the lateral line 

 canals and the ampullae of the lower jaw. 



VIII. The *auditory, the short nerve of the ear, arises 

 behind VII., and at once enters the auditory capsule. 



IX. The *fglossopharyngeal arises from the medulla, 

 posteriorly, in front of X., and passes back across the floor 

 of the auditory capsule to the first normal gill-cleft, over 

 which it forks. 



X. The *fvagus or pneumogastric has several roots. 

 Its branches are : A branchial trunk from which are given 

 off four branchials (each of which bifurcates) to the last 

 four gill-clefts ; the trunk continuing backwards as the 

 visceral to the heart and stomach. The lateralis, which 

 passes backwards along with and above the branchial 

 trunk, traverses the inner body wall to the posterior end 

 of the body, along the course of the lateral line, which it 

 supplies. 



Give a Short Description of (1) the Eye, (2) the Olfactory 

 Organ, and (3) the Ear of the Skate. 



( 1 ) The eye has the general structure described on page 203. 

 The lens is round, the upper part of the iris has a fringe. 

 There are no eyelids. 



(2) See page 205, also nostrils, page 219. 



(3) The ear is an otocyst or internal ear with three semi- 

 circular canals, an endolymphatic duct, and otoliths. (See 

 description given on pages 205, 206). 



Briefly Describe the Respiratory Organs of the Skate and 

 Dogfish. 



See page 211. 



Give an Account of the Venous System of Scyllium (Dogfish). 



There is a renal portal and a hepatic portal system, as 

 described on page 210. The posterior cardinal veins to- 

 gether form a large posterior cardinal sinus, which extends 

 forwards dorsally from between the kidneys. It is wide 

 in front and, near its opening at each side into the duct 

 of Cuvier, it receives a subclavian vein from the pectoral 

 region. 



