ORGANS OF SPECIAL SENSE 295 
168). The condition shown in Fig. 173, at eleven days seven- 
teen hours is substantially the same as in the adult. 
(d) Development of the Auditory Nerve and Sensory Areas of the 
Labyrinth. During the changes in the form of the labyrinth 
described in the preceding section, the lining epithelium has 
become thin and flattened except in eight restricted areas: viz., 
the three criste acusticw, one in each of the ampulle of the semi- 
circular canals, the macula utriculi, the macula saccult, the papilla 
Fia. 173. — Model of the auditory labyrinth of 
the right side of a chick embryo of 11 days 
and 17 hours; external view. (After Réthig 
and Brugsch.) Abbreviations as before. 
lagene, the papilla basilaris and the macula neglecta. Fach of 
these contains sensory cells ending in fine sensory hairs project- 
ing into the endolymph, or fluid of the labyrinth, and receives a 
branch of the auditory nerve proceeding from the acustie ganglia. 
Returning to an early stage to follow the development of sen- 
sory areas and nerves, we note first that the acustic ganglion from 
which the auditory nerve arises takes its origin from the acustico- 
