THE EPIBRANCHIAL GANGLIA OF LEPIDOSTEUS 15 
The whole ganglion in embryos of 10 mm. is not usually more 
than one-third as long as the geniculate, but this ratio varies, 
since the ganglion is sometimes triangular with the smaller end 
extending back into the truncus hyomandibularis. In older 
embryos the ganglion is always triangular and the posterior end 
grows posterior and ventral to the geniculate, thus simulating the 
relations in Menidia (Herrick, ’99), although the greater portion 
of the ganglion retains its position mesial to the geniculate. The 
fibers coming from the ganglion, mentioned in the preceding 
section as running out in the hyomandibular nerve, arise from 
the extreme posterior end of the ganglion and run into the hyo- 
mandibular on the ventral surface of the visceral fibers. The 
root arises here also and arches around the mesial surface of the 
geniculate ganglion and enters the medulla along with those of 
the dorso-lateral ganglion. 
The position of the ventro-lateral panelion in Lepidosteus 
differs from the position in Menidia (Herrick, 799) and in the 
embryo of Ameiurus (Landacre, 710) and in the Amphibia Cog- 
hill (02 and ’06). In the embryo of Ameiurus (56 hours) the 
ventro-lateral ganglion lies posterior to the geniculate, in Meni- 
dia posterior and mesial, while in the urodeles it is lateral (exter- 
nal) to the geniculate. There seems to be.no other case recorded 
where it is directly mesial to the geniculate. 
The fact that the nerve components have not been worked and 
consequently one cannot trace the ganglion back to this stage 
from an older series, renders the identification of this ganglion 
more difficult than in such cases as the Gasserian and dorso- 
lateral, where the ganglia are distinct and their nerves contain 
only one component which can be traced to its peripheral dis- 
tribution. 
Since, however, the placodal portion of the geniculate is quite 
distinct and its history can be traced, it becomes an important 
factor in the differentiation of the geniculate and ventro-lateral 
ganglia. Notwithstanding the rather unusual position of the 
ganglion identified as ventro-lateral, the following facts seem to 
warrant the identification: 
(a). The two ganglia are quite distinct histologically. | 
