210 G. W. BARTELMEZ 
closed at the caudal levels of the otic plate, but are still open in 
the region of the acousticofacial ganglion. Figure 2c represents 
the relations in a section through the caudal end of the right 
ganglion which is no longer in direct continuity with the neural 
fold except along its dorsal edge. From this well-fixed specimen, 
as well as from H637 which is equally good histologically, and 
from the description of Veit (18), it is obvious that there has 
been a loosening up of the ganglionic anlage followed by a separa- 
tion of the entire mass from the neural fold so that it has delami- 
nated before the two folds meet to form a tube. 
A word should be said here concerning this interpretation of 
Veit’s findings in his excellently preserved eight-somite embryo. 
His clear, accurate description and objective figures leave no 
doubt but that his caudale Ganglienleiste is what we interpret 
as the acousticofacial ganglion. Having but the one specimen 
at his disposal, Veit lacked the necessary data for identifying 
the subdivisions of the neural folds, and consequently his sug- 
gestions astothe fate of the Ganglienleisten are purely speculative. 
Turning now to the otic plate, no hint of an otic pit is to be 
found in either our eight- or nine-somite stages, nor did Keibel 
and Elze (’08) find any in their nine-somite embryo (N T No. 
4). In the eight-somite specimen (H87) the otic plate is dis- 
tinguished by a lighter peripheral zone. An additional feature 
appears in ‘Du Ga’ (nine somites) where Doctor Evans noted a 
peripheral brush border on the otic plate when he studied the 
series in 1910. In this embryo the plate appears as a boss on 
the side of the head. When we come to the eleven-somite 
embryo, H637, we find the invagination Just beginning. The 
histological appearance in this case is shown in figure 7, which 
represents a median section through this early otic plate. As 
we pass down from the dorsal ectoderm (from right to left in the 
figure), it will be seen that the pseudostratified condition of the 
ectoderm is preserved, but the distal moieties of the cells have 
elongated while the nuclei remained basal in position. Thus the 
clear peripheral zone is formed which characterizes the otic 
plate in all the older members of the series. When a particular 
cell begins to divide the nucleus migrates peripheralward and, as 
