340 



THE DOGFISH. PHYLUM CHORDATA 



in the olfactory capsule ; it opens externally by the nostril, but 

 has no internal opening. Its walls are thrown into vertical folds 

 covered with an epithelium which contains sense cells which 

 respond to odours. On the wall of the pharynx are taste buds 



VE Vn V VQb VEop 



gs Vaptsp sp VIlpsp. : VRi.m. \ Vmd 



Vnhd Vllem 



Fig. 257. — A diagram of certain cranial nerves in the dogfish. The nerves omitted 

 (III, IV, VI) consist of motor fibres to the eye muscles. Those shown supply 

 the visceral arches and certain other parts. They contain (a, shaded) visceral 

 motor (autonomic) and visceral sensory fibres ; {b, black) fibres from the 

 neuromast system (p. 344) and ear ; and (c, white), chiefly in X, some other 

 somatic sensory fibres from the skin. 



I'.. VII. X., Roots of the nerv'es ; V.md., V.mx., F.o^., mandibular, maxillar>', and superficial ophthalmic 

 branches of the fifth nerve ; V.op'., deep ophthalmic nerve, inconspicuous in the rough hound, but 

 large in many other fishes (p. 571) ; I'll.b., VlI.e.m., Vll.hd., Vll.i.m., VII.op., Vll.pal., buccal 

 external mandibular, hyoidean, internal mandibular, ophthalmic and palatine branches of the seventh 

 nerve ; VII.p.sp., Vll.pt.sp., pre- and post-spiracu'ar divisions of hyomandibular branch of seventh 

 nerve : X.I. X.v.. lateral line and main visceral branches o fthe tenth nerve ; g.s., gUl shts ;m. mouth ; 

 ■ip., spiracle. 



Fig. 258. — The head of a dogfish, seen from above with the right orbit opened. 



e. Eyeball ; 0.%.. o.s., inferior and superior oblique muscles ; r.e., r.i., r.int., r.s., external, inferior, internal 

 and superior recti muscles ; sp., spiracle ; //., optic nerve ; IV., fourth nerve. 



