membranous roof 

 over fourth ventricle 



terminal nerve 



asol sac 



superficial ophthalmic VII 

 buccal branch VII and V? 



palatine branch of VII 

 hyomandibular 

 branch Vlf 



soccus dorsalis and pineal body 

 optic lobe 



utriculus 



olfactory bulb 

 telencephalon 



diencepholon 

 nferior lobe 



pituitary 



horizontal canal 

 socculus 



posterior vertical semicircular conol saccus dorsalis 



')) 1 I I I mesencephalon 



^ _ .1 pineal bodv i 



cerebellum 



endolymphatic sac 



vertebral 

 O^h) /^vein 



spinoccipital 

 nerves 



olfactory bulb paraphysis 



endolymphatic sac 



vertebral vein 



chorioid plexus 



chorioid plexus over 

 fourth ventricle 



preoptic recess 



optic chiasma infundibulum 



pituitary 



Figure 13-9. Brain and cranial nerve roots of Protopterus. A, dorsol view with endolymphatic sac 

 and inner ear of right side included; B, ventral view; C, medial view of right half of brain. 



bulbs lie in contact with the olfactory capsules and are con- 

 nected by very long stalks with the rest of the telencephalon. 

 The cerebral lobes have a restricted ependymal septum as 

 in the young o( JVeoceratodus. The diencephalon has a pineal 

 organ above, and an infundibulum with bilateral inferior 

 lobes and a saccus vasculosus venlrally. 



The saccus vasculosus is an irregular evagination of the 

 rear wall of the infundibulum above the level of the pitui- 

 tary and is only slightly developed in this fish. It is perhaps 

 represented by the posterior recess of higher forms. Such a 

 saccus is well developed in actinopterygians and sharks. 



The pituitary of Latimena is drawn out anteriorly in the 

 direction of the sella turcica. The optic lobes form a single 

 medial mass behind which is a large cerebellum resembling 

 that of the shark or actinopterygian (i.e. with large facial 



lobes). The cerebellum lacks a valvula (see under actinop- 

 terygian) but has distinct auricles (restiform bodies). 



In its cranial nerves, Latimena is thoroughly fish-like. The 

 olfactory nerves are represented by many bundles of fibers. 

 There are well-developed superficial ophthalmic as well as 

 buccal mental and palatine branches of the seventh; the 

 ninth and tenth have typical sensory-line branches. The 

 hypobranchial musculature is served by branches of the 

 first spinals. 



Actinopterygians 



The olfactory bulbs lie in contact with the rest of the brain 

 in most actinopterygians, but in a few cases (Figure 13-10), 

 they are separated by long olfactory tracts from the cerebral 



392 



THE NERVOUS SYSTEM 



