200 MR. H. GRAY ON THE RETINA AND OPTIC NERVE, ETC. 
auditory nerve is now seen quite solid, and the vestibule presents a slight 
contraction near its centre. 
Fig. 17 . An embryo chick at the eighty-second hour, viewed from the dorsal aspect. 
The cavity of the fourth ventricle is distinctly seen, and on either side the 
rudimentary ear is shown in situ ; the contraction of the wall of the vesti- 
bule is more marked. 
Fig. 18. The ear of an embryo chick at the ninety-sixth hour. The vestibular con- 
traction is more marked, and a depression is observed at the extremity of 
the terminal vesicle, which subsequently forms one of the semicircular 
canals. 
8 IVilton Street, 
October \^th, 1849. 
