lobes (Gadus, Ameiurus, many cyprinids). The olfactory 

 bulbs may be solid and joined at the midline or separate 

 and contain ventricles connecting with the third ventricle 

 (Aciperuer). Much of the latter lies within the telencephalon. 

 The cerebral lobes are of the everted type, that is, the mem- 

 branous ependymal plate has been expanded to cover the 

 dorsal and lateral aspects of the large basal nuclei (Figure 

 13-5). These nuclei are joined by the anterior commissure, 

 which includes the pallial commissure. A small prepara- 

 physis may project upward from the telencephalic roof just 



anterior to the velum transversum. A velum is not always 

 present. 



The diencephalon is much restricted and not apparent 

 from the outside. Dorsally there is a large pineal body 

 joined to the posterior commissure by a pineal nerve. The 

 roof of the diencephalon is evaginated upward as a saccus 

 dorsalis and in part overlies the basal nuclei of the telen- 

 cephalon. The thalamic walls of the diencephalon e.\tend 

 down and back underneath the optic lobes. The infundibu- 

 lar evagination ends in a large saccus vasculosus. This is a 



optic lobe 



cerebellum 



telencephalon 

 olfactory 



medulla 



olfactory nerve (I) ^ i I ( 



olfactory bulb- 



pituitary 



saccus vasculosus 

 inferior lobe 



telencephalon 

 optic nerve (II) 



optic lobe 

 pituitary 



V-,,*'^^^ olfactory nerve (I) 



inferior lobe 

 saccus vasculosus 



olfactory bulb 



membronous roof of telencephalon 

 pineal body 



corpus sfriatus 



optic lobe 



occipitospinol nerve ( ^ 



volvula cerebellae 



posterior commissure 



torus longitudinalis 

 cerebellum habenula 



pineal body, 

 corpus striatus 



chorioid invaginotion 

 X 



cerebellum 



spinal cord 



anterior commissure 

 preoptic recess 



optic chiasma 



third ventricle 



fourth ventricle 



pituitary 



saccus vasculosus 



Figure 13-10. Brain and cranial nerve roots of the salmon. A, lateral view; B, dorsal view, mem- 

 branous roof on right half of forebrain removed; C, ventral view; D, medial view of right half. (After 

 Porker and Hoswell) 



THE CONDUCTING AND INTEGRATING SYSTEM 



393 



