704 



REPTILIA. 



compared with the bulk of the body. The appended figure (fig. 348), 

 which represents the brain of the Tortoise in three different aspects, 

 may easily be compared with that of the fish already given. The olfac- 

 tory lobes (c) might now be mistaken for prolongations of the anterior 

 extremity of the hemispheres ; they contain distinct ventricles, and of 

 course give origin to the olfactory nerves (o o) . The hemispheres (6) 

 are much more developed than in the last class ; their surface is always 

 smooth and without convolutions ; and they are hollowed out into capa- 

 cious ventricular chambers, in which are contained the corpus striatum 

 and choroid plexus (fig. 348, c), and the two sides are moreover brought 

 into communication by an anterior and posterior commissure. 



(1977.) The optic lobes (e) are as yet uncovered by the extension of 

 the hemisphere backwards, and each, when laid open, is found to enclose a 

 ventricle (fig. 348, c). The cerebellum (a) is still small, and consists but 



Brain of the Tortoise. 



of the median portion : behind it is a supplementary lobe (<?), extend- 

 ing over the fourth ventricle, as in Fishes. The student will easily 

 recognize the pituitary body (/) ; but neither this nor the origins of the 

 nerves present any peculiarity worthy of more particular description. 



(1978.) Taking the cerebral nerves in the order in which they arise, 

 we will now proceed briefly to trace their general distribution ; and this 



