264 Susan7ia Phelps Gage 



The precommissure , as seen upon the meson (Fig. 6), is 

 closely associated with the callosum, but a little distance on 

 either side three bands of alba appear (Fig. 51), the dorsal, the 

 callosum, the other two, parts of the precommissure (38). 



Diencephal. — Caudad of these cerebral commissures and 

 partly underlying them is "Cos. preoptic recess (Fig. 18), a slight 

 pocket in the endyma of the terma, which is continuous cau- 

 dad with the small recesses extending slightly into the roots 

 of the optic nerves. The cinerea about these processes is 

 continuous in the center of the nerve to its entrance into the 

 eye (Fig. 40), though no lumen is visible. 



The chiasma (Fig. 6) projects into the diaccele and does not 

 project below the general level of the ventral surface. Whether 

 the part marked chiasma also includes an inferior commissure 

 is not certain, but seems probable, as it has been found in 

 Triton alpestris and other urodeles. 



The infundibular region is large as in other low forms, and 

 has wide lateral processes of the cavity which underlie the 

 saccus. The saccus is formed by an irregular tubular arrange- 

 ment of cells, corresponding in appearance to the endymal cells 

 of the vicinity. The continuity with endymal cells is probable, 

 and is so represented in figure 23, but is not an absolutely 

 established fact. Among the tubules are capillaries. The 

 saccus is small in comparison with other amphibia and fishes 

 (cf. Fig. 93). In other series than those represented, no such 

 tubular arrangement was found, the roof of the infundibulum 

 being composed of a single, simple layer as though not thrown 

 into folds to form a saccus. 



The hypophysis is distinctly tubular and appears to be en- 

 closed by pia which separates it from the infundibulum, as 

 Osborn (37, p. 264)found in Cryptobranchus. Pigment cells 

 from the dura are also seen to intrude between them in frontal 

 sections (Fig. 50). In one heavily pigmented specimen such 

 cells completely separate the hypophysis from the infundi- 

 bulum. The floor of the infundibulum dorsad of the hypo- 

 physis is wide and composed of a single laj-er of endymal cells. 

 No indications of hypoaria as in fishes (Fig. 93) were found. 



The thalamus (Fig. 19-22, 37-38) is not sharply defined 



