174 JULIA WORTHINGTON. 
The dorsal ramus passes above the duct, innervating its 
dorsal surface ; the ventral ramus divides once more, giving 
off a small pharyngeal branch, that also sends tiny ramuli to 
the proximal end of the duct, and another branch that 
penetrates the duct at its distal end near the gill. In one 
specimen dissected I found on the first gill of the right side 
another fine branch that entered the anterior edge of the 
gill itself on the outer side. After the last gill sac the 
vagus enters m. constrictor cardiz, where it forms a 
dense plexus ; emerging from this it joins its fellow of the 
opposite side to form n. intestinalis impar, running 
caudad on the dorsal surface of the intestine, and sending 
fibres into it all along its course. 
THE SPINO-OCCIPITAL AND SPINAL NERVES. 
‘hese are complete nerves, such as are found in the higher 
forms, with a sensory ganglion lying just outside the sheath 
of the spinal cord, and sensory and motor roots. There is a 
difference between the first two nerves emerging immediately 
caudad of the cranial nerves and those that come after, and 
Firbringer’s division into spino-occipital nerves and spinal 
nerves is a good one, though | cannot place my division where 
he places his. Judging from his paper (M. Fiirbringer, 1897), 
he worked with mature adults only, aud imperfect material. 
This explains in part his confusion in regard to these nerves, 
for natural growth causes somewhat of a shifting of relative 
position outside the brain between the young animal and the 
mature adult. In fig. 14, for example, which was plotted 
from a specimen the diameter of whose head was about half 
the diameter of the adult head, acusticus 0b and the first 
spino-occipital nerve are seen to be separated by a consider- 
able space, but in the mature adult, such as fig. 1 was drawn 
from, the foramen of acusticus 6 is farther caudad with 
reference to the medulla—the medulla has apparently grown 
backward, carrying this nerve with it—and, as a result, when 
