224 FREDERICK TILNEY 
ward as the small prechiasmatic recess (38) which corresponds 
to the median portion of the supraoptic crest (41). This recess 
is continued laterad as a long canal extending for some distance 
above the optic nerve, the supraoptic recess (42). Both the 
prechiasmatic and supraoptic recesses are present in all the forms 
Fig. 3 Mesial view of forebrain reconstruction in adult cat. X 35. The 
unshaded area shows the cut surfaces of the reconstruction. 2, chiasmatic 
process; 4, chiasm; 1/1, infundibular stem; 12, infundibular canal; 14, infundib- 
ular process, pituitary surface; 27, mammillary body; 32, post-chiasmatic 
eminence; 33, post-chiasmatic recess; 34, post-infundibular eminence; 34, post- 
infundibular recess; 38, pre-chiasmatic recess; 40, recess of the nfundibular 
process; 41, supra-optic crest; 42, supra-optic recess. 
examined. Caudal to the prechiasmatic recess a large prom- 
inence rises from the floor of the ventricle in a position corre- 
sponding to the optic chiasm. ‘This is the chiasmatic process 
(2). From the caudal extremity of this process the floor falls 
sharply away and then extends backward for a considerable 
distance with a marked ventral inclination. The slope thus 
