VERTEBRATA. 415 
envelops the three pairs of vertebrate sense-organs. The 
notochord runs in the ventral wall of this membranous 
cranium as far as the mid-brain, terminating behind the 
infundibulum (Fig. 293, page 407). The first cartilages 
Fig. 299.—DEVELOPMENT OF VERTEBRATE CRANIUM. 
Dorsal View of Embryo. 
Nasal Sac. 
Trabecule. ) Rye 
Parachordals. 
Auditory Sac. 
Notochord. FI 
! 
Fig. 300.—DEVELOPMENT OF VERTEBRATE CRANIUM. 
(Later stage.) 
Internasal 
Septum. 
Nasal Capsule. 
Pituitary Fossa. 
Basis Cranii. 
Capsule. 
Basis Cranii. 
Notochord. 
to appear are two pairs of plates alongside of the noto- 
chord. The first pair extends forwards on either side 
of the infundibulum as the ¢vadecude, the hinder pair, 
