THE PINEAL SYSTEM OF FISHES 



209 



roof is not completely perforated, the canal being closed externally by 

 cartilage and thus ending blindly, as in Spinax (Fig. 49, Chap. 3, p. 73) 

 and the curious spoon-bill or paddle-fish {Polyodon) (Fig. 50, Chap. 3, 

 and Fig. 229, Chap. 23, p. 329). The end vesicle may reach the surface 

 in front of the cartilage at the prefrontal foramen, as in the thornback 



Fig. 145. — Sagittal Section through the Skull of Callorhynchus Antarcti- 

 ca, a Primitive Form of Fish allied to Chimaira. (After Parker and 

 Has well.) 



The pineal organ has been withdrawn from the surface and lies wholly within 

 the skull, its terminal vesicle lying at the apex of a recess — r.p. ; while the 

 endolymphatic duct of the vestibule, e.l.d., perforates the skull. 



=f--pn.b. 



Fig. 146. — Lateral View of the Brain of Callorhynchus Antarcticus> 

 showing the Pineal Body and Membranes in Place. 



Mm. : cerebellum. 



ch. plx. 1 , ch. plx.' 1 : membranous roof 



and choroid plexus of the third and 



fourth ventricles. 

 c. rest. : corpus restiforme. 

 crb. h. : cerebral hemisphere. 

 dien. : diencephalon. 

 lb. inf. : lobus inferior. 



me d. obi. : medulla oblongata. 



Nv. 

 olf. I. 

 olf. p. 

 opt. I. 

 pn. b. 

 pn. st. 

 pty. : 



optic nerve. 

 : olfactory bulb. 

 : olfactory stalk. 

 : optic lobe. 

 / pineal body. 

 : pineal stalk, 

 pituitary body. 



*4 



