290 THE DEVELOPMENT OF THE CHICK 
the hind-brain and bends in above it towards the middle line (Fig. 
168). The right and left sacci are, however, still separated by 
a considerable space. The walls of the saccus already form a 
large number of low folds, presumably glandular, the first begin- 
OX CTL LE ass 
ia. 168. — Transverse section through the head of a chick embryo of eight 
days in the region of the ear (photograph). 
C. a., Anterior semicircular canal. C. h., Horizontal semicircular canal. 
Caps. aud., Auditory capsule. Cav. Tymp., Tympanic cavity. Col., Colu- 
mella. Duet end., Endolymphatie duct. ex. au. M., External auditory 
meatus. Fis. Tub., Tubal fissure. Lag., Lagena. M. C., Meckel’s cartilage. 
Myel., Myelencephalon. N’ch., Notochord. p’l., Perilymph. Sac., Saceu- 
lus. Sae.end., Endolymphatie sac. Tub. Eust., Eustachian tube. Tymp., 
Tympanum. Utr., Utriculus. X., Sac derived from the inner extremity 
of the tympanic cavity. 
nings of which were visible on the sixth day. The form of the 
saccus and ductus endolymphaticus at a somewhat later stage 
is shown in the reconstruction (Fig. 173). 
