264 FREDERICK TILNEY 
evagination (18). Here growth has been more pronounced than 
in any other of the neighboring parts. This growth has affected 
the area immediately ventrad to the dorsal infundibular evagi- 
nation which in this stage of 70 mm. had already shown signs 
of expansion. The result of the growth is the formation of an 
infundibular process (13) which consists of a smooth, membran- 
ous, but as yet non-vascular, dorsal surface not in contact with 
Fig. 29 Mesial view of brain reconstruction of 100 mm. Mustelus. X 25. 
The unshaded area shows the cut surfaces of the reconstruction. 2, chiasmatic 
process; 3, cerebellum; 4, chiasm; 7, epiphysis; 13, infundibular process; 14, 
infundibular process, saccular surface; 15, infundibular process, pituitary sur- 
face; 24, mid-brain; 27, mammillary body (posterior lobe); 32, post-chiasmatic 
eminence (lobus inferior); 33, post-chiasmatic recess (recess of inferior lobe); 
36, post-infundibular evagination; 40, recess of infundibular process; 4/1, supra- 
optic crest; 42, supra-optic recess; 44, telencephalon; 47, velum transversum. 
the pituitary gland, the saccular surface (14) and a thicker sur- 
face in contact with the gland, the pituitary surface (15). In 
the 100 mm. Mustelus the saccular surface presents no sign of 
convolution or blood vessels; in the 300 mm. Mustelus the ten- 
dency toward the production of complicated diverticula in this 
surface is evident, as well as arapidly advancing vascularization. 
These changes mark the inception not only of the diverticula 
sacci vasculosi, but also of the rich blood supply which gives the 
saccus vasculosus its name. In addition to the diverticula 
sacci vasculosi there is a portion of the recess of the infundibular 
