DS PA FREDERICK TILNEY 
shows clearly the median post-chiasmatic groove and the two 
lateral processes, one on either side of this groove. More marked 
is the change in the caudal portion of the infundibular region 
where the infundibular process is now well formed, and con- 
nected with the floor of the diencephalon by a short, broad stalk, 
the infundibular stem (//). The infundibular process itself 
7 
Fig. 20 Mesial view of forebrain reconstruction of chick of 9 days and 19 
hours. X 50. The unshaded area shows the cut surfaces of the reconstruction. 
2, chiasmatie process; 3, cerebellum; 4, chiasm; 7, epiphysis; 9, foramen of 
Monro; 11, infundibular stem; 13, infundibular process; 24, mid-brain; 26, 
mammillary recess; 27, mammillary body; 32, post-chiasmatic eminence; 33, 
post-chiasmatic recess; 36, post-infundibular eminence; 38, pre-chiasmatic 
eminence; 4/, supra-optic crest; 42, supra-optic recess; 44, telencephalon. 
presents a median expanded portion, from which there extends 
to either side a slender lateral process. This formation corre- 
sponds closely to the conditions in the infundibular process of 
Mustelus at the stage of 50 mm. .The ventricular cavity extends 
through the infundibular stem and upon entering the infundib- 
ular process rapidly expands into a number of branching diver- 
ticula. These diverticula are confined largely to the dorsal 
surface of the infundibular process and extend from its median 
