1 14 Journal of Comparative Neurology 



DESCRIPTION OF FIGURES. 

 Plates II, III and IV. 



Fig. 1. Dorsal view of the brain of an adult Chelydra, x 3, drawn with pia 

 only adhering. Shows the segmentation of the brain, its length compared with 

 the transverse diameter, the origin of the nerves and the slight development of 

 the post-gemina and "inter-optic lobes." 



Fig. 2. Ventral view of same. Shows the lobed condition of the cere- 

 brum and the general narrowness of the ventral regions when compared with 

 the dorsal portion of the brain. Also ectal nerve origins. 



Fig. 3. Lateral view of same. Drawn to show the segmentation of the 

 brain which is revealed most plainly from this view. In these three figures the 

 metatela is not shown. 



Fig. 4. Dorsal view of the brain of an embryo Chelydra nearly ready for 

 hatching, x 4. Shows a more compact structure but does not exhibit the great 

 amount of flexure that really exists in the brain at this time. 



Fig. 3. Dorsal view of the epencephal and metencephal. Showing the 

 metatela in its natural position. Enlarged the same as figures I and 3. 



Fig. 6. A mesal view of the diencephal and mesencephal of Chelydra to 

 show the relations in those very complex regions. In this figure no membranous 

 portions are shown. It shows the position of the commissures, the relations of 

 the different cavities, main sulci etc. 



Fig. 7. A mesal view of the entire brain of the great sea turtle, x 2. 

 Shows in addition to the features shown by figure six membranous portions of 

 the brain roof, especially the metatela and the three parts of the diencephalic 

 dorsal outgrowth. The larger relative size of the cerebrum and cerebellum are 

 to be noticed. 



Figs. S-ij. A series of transections of the metencephal of an adult Chel- 

 ydra, arranged with the caudal sections first. 



Fig. 8. Shows a transection of the metencephal at its caudal limit, the 

 caudal continuation of the metaccele, as three pockets, the outlines of the ci- 

 nerea and the general distribution of the fibrous columns. 



Fig. q. Showing blending of pockets of metaccele and the union with dor- 

 sal furrow and myeloccele, also a slight change in the position of the dorsal 

 column. 



Fig. 10. Shows widening of the metaccele, a further change of form of the 

 dorsal column and the projection of the dorso-lateral portion of the general 

 parietes, also the beginning of the reticular area. 



Fig. 11. Carries these changes still farther. In addition is shown the cen- 

 tral lophius and several secondary sulci in the floor of the metaccele, while the 

 ventral bundle becomes plainly the posterior longitudinal fasciculus. 



Fig. 12, In this the widening of the metaccele is very great with conse- 

 quent changes in position of fibrous columns; the reticular area is greatly in- 

 creased, while the dorsal cornu is much reduced. A large nucleus is shown in 

 the raphe. 



