108 JOHN BEARD. 
actual fusion of the vagus ganglia with the sensory thickening, 
does not ascribe to the skin any part in the formation of the 
ganglia. 
Like Van Wijhe, I cannot find in the vagus outgrowth 
itself any real segmentation in its earliest stages. The first 
outgrowth from the neural crest (fig. 33).is a broad unin- 
terrupted band stretching from just behind the glossopharyn- 
-geal, which it almost joins, to a considerable distance backwards. 
Like other posterior roots, this outgrowth grows outwards 
and downwards towards the portion of epiblast just above the 
second, third, fourth, and fifth branchial clefts, which are now 
just forming (fig. 33). Here the epiblast forms a longish 
seusory thickening, with which the vagus fuses. 
Portions of the vagus pass on (fig. 34) behind the rudiments 
of each of the above-mentioned clefts, and form, as in other 
cases, the post-branchial nerves. 
At the point of fusion with the skin, cells are proliferated 
from the epiblast to form the ganglia. 
Soon, as pointed out by Van Wijhe, we get the ganglion of 
the first vagus cleft separated from the rest of the mass and 
fused with an isolated thickening above the second true branchial 
cleft. 
For the rest of the vagus there is usually only one ganglionic 
mass, which, however, ventrally, and by its post-branchial 
branches, shows a division into three portions. This mass lies 
over the last three clefts, and is to be regarded as made up of 
the fused ganglia of the three branchial sense organs of these 
clefts, with the addition, however, of rudiments of nerve 
elements of a certain number of clefts, which have disappeared ; 
and even in the ontogeny hardly present traces of their former 
existence. In Torpedo, however, as first noticed by Wyman,lt 
there is a rudiment of one cleft which never breaks through to 
the surface, and hence which is never functional.? The rudi- 
Wyman, “Observations on the Development of Raja batis,” ‘Mem. 
Amer. Acad. of Arts and Sciences,’ vol. ix, 1864. 
2 This paper of Wyman’s was not accessible, and the statement in the text 
is given from Balfour’s ‘ Embryology,’ vol. ii. 
