Frederic T. Lewis 215 
which is found a low elevation, the tuberculum impar of His. Kallius, 
oz, p. 42, has named this pair of mandibular elevations the lingual 
folds, and states that they form almost the entire body and tip of the 
tongue. The tuberculum impar is the source of the posterior part of 
the lingual body and of the septum. <A shallow transverse groove still 
marks the fusion of tuberculum impar and the root of the tongue. The 
thyroid duct which opened into this groove has become obliterated, and 
the circumyallate papilla which are to develop along its course have 
not yet appeared. That the root of the tongue is formed by a fusion 
of the second and third arches, as stated by His, 85, p. 65, could hardly 
be determined at this stage. 
Behind the tongue there is a short, low, bilobate protuberance, the 
epiglottis. Beyond this the ventral will of the pharynx presents a 
round, dorsally directed elevation, which soon becomes indented in the 
median line. Thick conical masses, the arytenoid folds, appear on 
either side of this groove. The notch between them becoines a long, 
slender slit. The trachea, after separating from the cesophagus, con- 
tinues in this slit-like form, its lateral walls being in close contact, except 
at their dorsal end, where a minute passage exists. Further caudad 
the ventral prolongation disappears, and the trachea is then a simple 
tube, Plate III. The subsequent development of the larynx has not 
been adequately described. 
The oral cleft, forming one of a pair of lateral wings at the begin- 
ning of the digestive tract, is represented in Plate II. The auditory 
cleft rises dorsal to the pharyngeal wall, and passes to the auditory 
groove. It does not open to the exterior. Its internal orifice is drawn 
in Plate IV, in which it is seen to end behind a conical mass pendant 
from the side of the pharyngeal roof. The anterior part of the Eusta- 
chian opening meets the beginning of the oral wing. 
The second pharyngeal pouch runs posteriorly outward, parallel with 
the course of the pharynx. It opens freely into a well marked external 
groove which subsequently deepens and separates the lower jaw from 
the neck. There is no indication of a “ Verschlussplatte ” in series 5; 
in series 518, an oblique plate is present on both sides, but appears to 
be broken through. In a 10-mm. pig, the clefts opened to the exterior 
hut remnants of the plates existed. As yet no indication of the tonsils 
appears in connection with the second cleft. 
The third pouch is a slender tube passing outward, at right angles 
with the pharynx to its small “ Verschlussplatte.” Just within the 
plate it gives rise to a slender tube passing ventrally, parallel with the 
external groove of the second cleft. This diverticulum may represent 
