308 ZOOLOGY SECT. 



optic tracts (o.t.) continued into the optic nerves. Behind the optic 

 tracts the floor is produced downwards into a tubular process, the 

 infundibulum (inf.), ending below in a rounded body, the pituitary 

 body or hypophysis (pty.). The roof is produced into a median 

 process, which is divided into two parts, one corresponding to 

 the epiphysis or pineal body, while the other has connected with 

 its distal extremity an eye-like structure, the parietal organ or 

 pineal eye (Fig. 916), lying in the parietal foramen. The mid- 

 brain consists dorsally of two oval optic lobes (corpora bigemina). 

 (o. I.) and ventrally of a mass of longitudinal nerve-fibres, the 

 crura cerebri (c. c.), passing forwards to the fore-brain. Each optic 

 lobe contains a cavity (optoccele) communicating with a narrow 

 passage leading from the diacoele to the metacoele. The cerebellum 

 (cb.) is, like that of the Frog, of small size, being a small antero- 

 posteriorly flattened lobe overlapping the anterior portion of the 



metacoele. The meten- 

 cephalon (medulla ob- 

 longata, m. o.), broad 

 in front, tapers behind 

 to where it passes into 

 the anterior portion of 

 the spinal cord. The 

 metacosle is a shallow 

 space on the dorsal 

 aspect of the medulla 

 o f/i oblongata, overlapped 



in front for a short 



FIG. 916. Side view of the brain of Lacerta ocellata, distance by the C6re- 



showing the relations of the pineal eye. cbl. cerebel- v n j "U "U ' J 



him; epi. epiphysis; inf. infundibulum ; opt. I. optic DelJUm, ana 



lobes; opt. n. optic nerves ; paren. parencephalon ; pin. nrkimYVirl rml-sr VT7 +Vn 



pineal eye ; st. strand connecting eye with epiphysis. ' mv DV Ine 



(After Baldwin spencer.) pi a mater, containing 



a network of vessels, 



the choroid plexus of the metacoele. At the point where medulla 

 oblongata and spinal cord meet is a strong ventral flexure. 



The spinal cord is continued backwards throughout the length 

 of the neural canal, becoming slightly dilated opposite the origins- 

 of the two pairs of limbs, and tapering greatly towards the 

 posterior end of the tail. 



The cranial nerves resemble those of the Frog as regards their 

 origin and distribution in most respects, the principal difference 

 being that there is intercalated in front of the hypoglossal a 

 spinal accessory, and that the hypoglossal arises from the medulla 

 oblongata, not from the spinal cord, and is therefore a cranial 

 nerve 



The nasal cavities (Fig. 917) open at the extremity of the snout 

 by the external nares, and into the cavity of the mouth by a pair of 

 slit-like internal nares situated near the middle line of the palate.. 



