20 F. L. LANDACRE 
general visceral and placodal portions to each other. The gen- 
eral visceral portion sometimes extends farther forward than the 
placodal portion, sometimes both general visceral and placodal 
portions are of equal length and the anterior end of the ganglion 
is split (figs. 14, 15). In all series of this stage the anterior end 
consists of a mesial rounded portion and of a lateral spur resting 
on the endoderm of the hyoid gill pocket and extending somewhat 
dorso-laterally toward the epidermis (figs. 16 to 20). A portion 
of the median rounded mass and all of the lateral spur are derived 
from the placode. The manner in which the placodal portion 
joins the general visceral varies in different embryos somewhat. 
The visceral cells may lie like a cap dorsal, mesial and sometimes 
lateral to the placodal cells. In later stages the placodal cells 
are usually surrounded by the general visceral cells in this manner, 
but the condition shown in figs. 14 to 21 is the usual one in the 
10 mm. stage, so that the placodal portion of the ganglion begins 
at the extreme anterior end of the ganglionic mass (fig. 14) 
becomes broader a few sections posterior to this point and pos- 
sesses a large lateral spur (figs. 17 to 19) and disappears a few sec- 
tions posterior to the anterior end of the ventro-lateral lateralis 
VII. 
The placodal portion of the ganglion can be distinguished 
from the general visceral by the difference in staining reaction, 
the placodal portion usually being much darker (fig. 26) and 
can be distinguished further, by the arrangement of the cells, 
the placodal cells being elongated in the direction in which they 
have moved into the ganglionic mass. The most uniform and 
most easily recognized characteristic is that of color (figs. 26, 28, 
30, 31). 
Posterior to the placodal portion of the geniculate ganglion 
we find the general visceral and ventro-lateral and dorso-lateral 
portions only (fig. 27). The ventro-lateral ganglion lies mesial 
and quite close to the geniculate and usually imbedded in it. It 
is a short round ganglionic mass with its cells usually arranged in 
a rosette with the nuclei situated peripherally. The geniculate 
ganglion has a totally different appearance, consisting of a rather 
dense mass of cells irregularly arranged and having very indefin- 
