306 THE DEVELOPMENT OF THE CHICK 
sets in about the eighth day, and the early thickening of the 
epithelium of this part already referred to is undoubtedly the 
first stage in the process. 
The development of the musculature of the tongue has not 
been followed. The development of the skeletal parts is con- 
sidered under the head of the skeleton. 
Oral Glands. The following oral glands occur in the hen: 
1, lingual glands; 2, mandibular glands; 3, glands opening at 
the angle of the mouth; 4, palatine glands in the neighborhood 
of the choanz. The only account of their development known 
to me is the brief one of Reichel. All the glands begin as solid 
ingrowths of the mucosa, which may branch more or less, and 
secondarily acquire a lumen. Their development begins relatively 
late. The mandibular glands appear first on the eighth day as 
a series of solid ingrowths of the mucosa extending on both sides 
of the base of the tongue forward to near the mandibular sym- 
physis. They are still mostly solid on the eleventh day, and 
very slightly branched, if at all. The lingual glands arise beneath 
the lateral margin of the tongue and grow up on each side of the 
lingual cartilage towards the upper surface where they branch 
out. They begin to form on the eleventh day. No glands form 
on the upper surface of the tongue. The glands of the angle of 
the mouth appear on the eleventh day, in situ, as slight epithelial 
ingrowths. Their further history has not been followed. An- 
terior and posterior palatine glands can be distinguished; the 
first in front of the choanz, the latter at the sides of and behind 
the choane. They begin to appear after the eleventh day. 
II. DrrRIVATIVES OF THE EMBRYONIC PHARYNX 
The pharynx, which is such an extensive and important region 
of the early embryo owing to the development of the visceral 
arches and clefts, becomes relatively much reduced in the process 
of development, though of course it becomes much larger abso- 
lutely. In the adult it is a somewhat ill-defined cavity from 
which the cesophagus leads away posteriorly, and which is con- 
fluent with the mouth anteriorly. The tubal fissure opens in 
its roof and the glottis in its floor. During the course of develop- 
ment, however, certain more or less persistent structures form 
from its walls, or from the epithelium of the pouches. Although 
these are relatively inconspicuous organs in the adult, they are of 
