No. 408.] STUDY OF MAMMALIAN EMBRYOLOGY. 92I 
hind-brain. The section is bounded by the thin layer of epider- 
mis, between which and the brain-walls there is a large amount 
Jug." 
F.b. 
Fic. 3. eis embryo of 12.0 mm. No. ransverse section 195. Æc., ectoderm; /.4., fore- 
; Jug.', Jug.", ge vein; un infundibular gland; Mad., medalla oblongata ; 
oe Fotocys bp Str., striae acusticze; Ven., cavity of — * trigeminal ganglion ; 
Bede 9, a pharyngeus; 70, vagus; ccessarius; 77., third 
vende ofthe brain. x 22 dia 
of mesenchymal tissue. Alongside the hind-brain lie a series 
of important structures imbedded in the mesenchyma, which 
