CRANIAL NERVES OF SIREN LACERTINA 307 
it has not been possible to determine with certainty, but they 
have the histological characteristics of general cutaneous fibers, 
although apparently coming from the communis portion of 
the third group of rootlets as mentioned above. No general 
cutaneous fibers, however, have been identified in the ramus 
posttrematicus IX. The dorsal part of the vagus portion of the 
ganglionic mass is composed of the large lateral line ganglion 
cells. The ganglion cells of the general cutaneous constituent 
are situated for the most part anteriorly, postero-dorsal to the 
IXth portion of the ganglionic mass. The ventral part of the 
ganglion is composed mostly of communis ganglion cells. Within 
the ganglionic mass it is impossible to follow and differentiate 
the constituents of the roots already mentioned with very much 
exactness. The fibers of the IXth root all pass into the glosso- 
pharyngeal nerve. General cutaneous fibers from the vagal roots 
enter the base of the pretrematicus IX on their way to the 
ramus communicans cum faciali. The writer finds no evidence 
of general cutaneous fibers in the peripheral portion of the ninth 
- nerve. The constituents of the third and fourth groups of rootlets 
are so much mixed that the sensory components are with difficulty 
differentiated in the ganglion itself. The motor fibers of the 
fourth group of rootlets appear to enter mostly, if not exclu- 
_ sively, the ramus intestino-accessorius X. 
3. The ramus communicans cum facralr 
Driiner considers this ramus in Siren, as well as in other 
Urodela examined by him, except Siredon (Amblystoma), to 
be exclusively motor. He bases his opinion largely upon theo- 
retical grounds: that muscles belonging primarily to the glosso- 
pharyngeal territory have come to be innervated by the jugularis 
VII through fibers which are in reality (in the opinion of Driiner) 
furnished by the ramus communicans. In Amblystoma Coghill 
has shown that the ramus communicans is composed of general 
cutaneous and communis fibers. Driiner himself admits that 
there are communis fibers in the communicans of Siredon. Miss 
Bowers describes the same nerve in Spelerpes as general cutaneous 
