GANGLIA AND NERVES OF SQUALUS 43 
glionic complex which is the usual place of origin of this nerve 
in embryos. All the embryos at my disposal from 20 mm. to 
30 mm. have been examined repeatedly with the greatest care 
and no nerves pass dorsally to the ectoderm from the proximal 
portion of the ganglion. ‘This is true of the 25 mm. embryo, 
where the mass of cells identified above as the jugular ganglion 
is best isolated. 
There are, however, in the 22 mm. and 25 mm. embryos sev- 
eral minute processes arising from the posterior and dorsal bor- 
der of the root of X which could not be followed farther than 
the width of one ganglion cell but present the appearance of 
very immature nerves. They are constant in neither number 
nor position and vary in both on opposite side of the same 
embryo and are not included in the reconstruction in figure 1. 
In the 30 mm. embryo a nerve arises apparently from the root 
of X near the first spinal ganglion but not from it and runs, 
cephalad passing along the ventral border of the anterior end of 
the primordium of the somatic musculature then runs to the 
ectoderm of the mid-dorsal region of the head where it ends 
just posterior to the area supplied by the most dorsal rami of 
supratemporalis IX and X. ‘This nerve is very small and could 
not be located on the opposite side of the same specimen. It 
has the usual distribution of a r. auricularis In embryos except 
that it arises too far posterior. 
There is in addition in all embryos from 22 mm. to 30 mm. in 
length a nerve (figs. 1, 9, 10 and 11, R.Aur.) running out with 
the lateral line ramus arising from the ganglion lateralis X»._ It 
arises with the lateral line nerve but soon separates from it and 
pursues a course caudad parallel to it but slightly more ventral 
in position than the lateral line nerve to a point near the third 
spinal ganglion, when it turns dorsal and is distributed to the 
ectoderm. Its relation to the lateral line nerve is not entirely 
clear since it seems to form anastomoses with it but some of the 
fibers of this nerve are distributed to the ectoderm at points 
where there are no lateral line primordia at the stages studied. 
The fibers seem to pursue a course from the distal end of the 
jugular ganglion proximally along the dorsal border of lateralis 
