BRAIN. 



157 



back that they almost touch the sides of the medulla, and for the double roots of the 

 olfactory nerves. 



REPTILES. There is considerable range in the brain of the reptiles, all show- 

 ing an advance over the amphibians in having the cerebrum larger than the optic 

 lobes; in having, in the pallium, besides the basal layer of gray matter, a distinct 

 cortical layer of nerve cells; the well developed hippocampus; while the olfactory 

 lobes may either be sessile upon the hemispheres or differentiated into tracts and 

 bulbs. 



FIG. 159. FIG. 160. 



FIG. 159. Brain of Iguana tuberculata (Princeton, 2293). Compare fig. 172. 



FIG. 160. Side and dorsal views of brain of young alligator, after Herrick. c, cere- 

 brum; d, cerebellum; e, epiphysial structures; h, hypophysis; i, infundibulum; ol, olfactory 

 lobes; II-XII, cranial nerves. 



The greater size of the cerebrum and the large optic lobes result in covering the 

 diencephalon so that it is scarcely visible from above (figs. 159, 160). Infundibulum 

 and hypophysis are well developed, but the sacci vasculosi are rudimentary and the 

 inferior lobes are inconspicuous. The epiphysial structures reach their highest 

 development in this group. In most species the parietal organ is rudimentary, but 

 in many lizards and especially in Sphenodon it penetrates the roof of the skull and 



