PISCES 239 



otolithic particles surrounded by a jelly. The nasal sacs are cup- 

 like cavities with plaited cells. They serve for sinell only. The 

 sensory tubes are best seen on the ventral surface, where they lie 

 just under the skin. At their internal ends lie ampullae, con- 

 taining sensory cells. At their outer ends there are pores. It is 



r — No sat capsule 

 j^-Olfacfory bulb 



Olfactory ^folk 



Olfactory lobe 



Cerebrurn 



■ Tfialamencepbaton 



^—•f Opffc nerve 



• Optic chioa/na 

 •Opfic tracf 

 -Inferior fobe 

 -Pituitary 



-Oculomotor nerve 



• Trochlear nerve 



-ffesfiform body 



^^^/ - TriqemirtQl nerve 



- S^ m^ -^ Abducens nerve 



•■Facial nerve 



•Auditory nerve 



tvledulla oblon<jafa 



Closso pfiarync^eal nerve* 



Spinal cord 



— Pneumo<jastric nerve 



Fig. 116. Ventral view of dogfish brain, showing cerebral nerves. (Drawn by W. J. 



Moore.) 



probable that they are organs partly of touch and partly of 

 " chemical sense." The lateral line organs detect vibrations of low 

 frequency. The ear, the lateral line, and a pre-auditory sensory 

 patch are developed from a thickening of the ectoderm. The 

 ectodermal rudiments of the otocyst and the lateral line are in some 

 cases continuous at first. Sensory cells in the canals closely 

 resemble the sensory cells of the ear. (See p. 259.) 



