480 ‘LANDACRE AND McLELLAN 
The presence of two branchial nerves arising from this ganglion 
would suggest that it represented two branchial ganglia fused. 
However, there is some doubt as to whether the fibers of the 
second branchial nerve arise in this ganglion or partly in this 
ganglion and partly in the second visceral ganglion. 
(c) The second visceral X ganglion, unlike the glossopharyn- 
geal and the first visceral X, lies with its long axis at right angles 
to that of the body. It gives rise to two chief nerve trunks; one, 
the ramus intestinalis and a smaller ramus which probably con- 
tains branchial fibers. The question as to the exact position of 
the branchial ganglia in these two visceral ganglia cannot be 
definitely settled without further examination of earlier stages. 
A eareful study of a close series of embryos will probably show 
definitely the number and position of the epibranchial placodes 
and their position in the visceral ganglia, thus determining the 
number of branchial ganglia in this complex and their location. 
6. The failure to distinguish special visceral or gustatory 
ganglia in Rana in the stages studied is not to be interpreted to 
mean, of course, that they are absent or cannot be isolated. As 
mentioned in the introduction, this paper is preliminary to a 
study of the mode of origin of the cerebral ganglia in the frog. As 
a matter of fact, epibranchial placodes are present in the stages 
earlier than 8 mm. and well defined and seem to behave much as 
they do in Ameiurus and Lepidosteus. It is hardly probable 
that they will be so distinct or can be followed to so late a stage 
as in Lepidosteus, since they are not recognizable in the 8 mm. 
stage. Neither is it likely that the frog will furnish such definite 
evidence as to the character of placodal ganglia as did Ameiurus, 
since all nerves arising from the IX seem to contain both general 
visceral and special visceral fibers, whereas in Ameiurus they seem 
to contain only special visceral fibers. 
7. The results of the present paper emphasize the immense 
importance of having access to a large number of stages taken at 
close intervals from the same lot of eggs, if one is to reach safe 
conclusions in regard to the composition and origin of cerebral 
ganglia. All ganglia, particularly those derived from the neural 
crest, in their early stages are more or less ill defined; following 
