262 Susanna Phelps Gage 



the cerebellum being nowhere visible from the surface. The 

 metaplexus forms a conspicuous object on the dorsal side. 

 The supraplexus is not very large and lies between the caudal 

 angles of the hemicerebrums ; immediately behind it are the 

 habenae and the small epiphysis. On the ventral side, the 

 diencephal with its connected infundibulum and hypophysis, 

 covers the floor of the mesencephal. 



In the mesal view, the cerebellum appears ; the thickness 

 of the parietes, the relations of commissures, cavities and plex- 

 uses are also seen. 



In the figures, interrupted lines indicate the extent of the 

 cavities which are wide, especially in the dorso-ventral direc- 

 tion, as seen in sections (PI. III). The constrictions of the 

 cavities are so great, that sections, which like those of PI. I 

 show them as continuous from cephalic to caudal extremity, 

 are rare. 



Rhmencephal. — As in other urodeles the olfactory lobes 

 are entirely separate from each other. From the ectal surface 

 there is little appearance of constriction separating the olfac- 

 tory lobes from the hemicerebrums. The cavities show a slight 

 dorso-lateral constriction (Fig. 5,) in frontal view seen in fig- 

 ure 37. A decided angle exists at the caudal boundary of 

 the rhinocoele (Fig. 35, 41), which corresponds almost precise- 

 ly with the caudal boundary of the second olfactory nerve 

 root. Hence it is seen that the rhinencephal is nearly equal 

 in length to the prosencephal. 



The paraplexus intrudes slightly into the rhinocoele. The 

 extensive area occupied by the external origin of the olfactory 

 nerve roots is noticeable and the fact that a fold of pia in- 

 trudes between the two roots. 



Cinerea covers nearly the entire surface of the olfactory 

 lobes. But it is a remarkable fact that at certain points the 

 ectal cinerea is continuous with the ental (Fig. 14-15, 35-37, 

 41) as though the embryonic condition were preserved. 



Proseiicephal. — The hemicerebrums have a decided though 

 short caudal projection (Fig. 19-22), beyond the portae, contain- 

 ing a spur of cinerea (Fig. 36, 42) which corresponds in position 

 with a similar spur which Edinger (11, p. 20) has found in rep- 



