390 H. W. NORMS AND SALLY P. HUGHES 



the epibranchial cartilage, and two on the ventral region along 

 the ceratobranchial cartilage. This number is subject to varia- 

 tion. The ganglia vary greatly in size and distinctness. In 

 most instances they are situated on the bases of small branches 

 of the posttrematic ramus, these small branches almost always 

 containing motor fibers, so that motor nerves seem to arise from 

 the ganglia. Non-medullated fibers connect with the ganglia 

 and form conspicuous components of the nerve branches con- 

 nected with the ganglia. In some instances non-medullated 

 fibers connect adjacent ganglia external to the post-trematic 

 ramus, forming semblances of plexuses. The non-medullated 

 fibers, when they occur in large enough numbers, are in marked 

 contrast to the medullated (lightly) fibers of visceral sensory 

 nature. But in general the sympathetic fibers cannot be traced 

 far from their ganglia because of the diffuse arrangement. No 

 sympathetic ganglia were found by the writers on the pretre- 

 matic and pharyngeal rami of the branchial nerves. 



The only reference the writers have found mentioning sympa- 

 thetic ganglia upon branchial nerves is one by Allis ('01), who 

 finds on the hyomandibular trunk of Mustelus a ganglion of 

 small cells, from which pass four small nerves into the second 

 dorsal constrictor muscle. The writers find this ganglion in 

 Mustelus as Allis has described it; also other small ganglia on 

 the more ventral branches of the same nerve. 



As the hyomandibular trunk of Squalus passes dorsolaterally 

 at the anterior wall of the spiracle the visceral sensory fibers are 

 seen collected at the dorsolateral border of the nerve, the motor 

 element at the ventrolateral edge, the main portion of the trunk 

 being lateral line. In the transition from the anterior wall of 

 the spiracle over to the posterior wall some of the visceral sens- 

 ory fibers of the nerve are seen to pass around on both sides to 

 the region of the motor fibers. Slightly farther ventral to this 

 appear the sympathetic ganglia on small motor branches given 

 off to the second dorsal constrictor muscle. Upon some of these 

 branches (five or six) there are small ganglionic masses, the cells 

 of which are much smaller than the smallest cells of the ordinary 

 cranial nerve ganglia. Non-medullated strands, external to the 



