242 FREDERICK TILNEY 
giving evidence that the growth going on in this structure at 
this stage is in a cephalic direction. The optic peduncle has 
increased in size, due to the addition of more optic fibers. 
Al y 
ME aA if in 
I) : ili 4 
H y 1 LF 
ail can C5 
40 
Fig. 12 Mesial view of forebrain reconstruction of 30mm. cat embryo. X 50. 
The unshaded area shows the cut surfaces of the reconstruction. 2, chiasmatic 
process; 4, chiasm; 5, corpus interpedunculare; 7, epiphysis; 9, foramen of 
Monro; //, infundibular stem; 1/2, infundibular canal; 13, infundibular process; 
20, lamina terminalis; 25, mammillary region; 32, post-chiasmatic eminence; 
33, post-chiasmatic recess; 34, post-infundibular eminence; 35, post-infundib- 
ular recess; 39, paraphysis; 40, recess of the infundibular process; 41, supra- 
optic crest; 42, supra-optic recess. 
Cat embryo of 30 mm.; Specimen No. 585 (fig. 12). The fore- 
shortening of the diencephalic floor observed in the embryo of 
15 mm. is here less pronounced, although the lamina terminalis 
(20) retains its vertical position. The prechiasmatic and supra- 
optic recesses are more pronounced, due to the increase in size 
of the chiasmatic process (2). The chiasmatic fibers are present 
in large numbers in the ventral aspect, while the dorsal extension 
