CEANIAL NERVES OF CAECILIANS 521 



at the level of the choana as stated above, is a large nerve {op.l) 

 one or more of whose twigs interweave indistinguishably with the 

 small nerve sent forward through the Gasserian ganglion from 

 the facialis. The main portion of this first branch {op.l) con- 

 tinues anteriorly and laterally, soon running in a groove and 

 canal in the frontal bone (fig. 10), then between the frontal and 

 the maxilla (fig. 9), and eventually in the maxilla at the lateral 

 dorsal border of the nasal chamber (fig. 8), and thence on the 

 dorsal wall of the tentacular canal (figs. 4, 3), from which course 

 it sends out cutaneous branches to the side of the head, being 

 finally distributed to the tentacular sheath and to the skin in 

 the region of the tentacle, its fibers commingling and anastomos- 

 ing with the fibers of the medial branch of the ramus maxillaris. 

 The sensory innervation* of the tentacle itself is from this lateral 

 branch of the ramus ophthalmicus profundus, and not from the 

 facialis, as stated by Marcus. 



A second large branch {op. 3) leaves the main trunk as the 

 latter is passing through the canal in the dorsal ethmoidal 

 region, and passes anteriorly along the dorsal wall of the nasal 

 chamber (figs. 9, 8), farther anteriorly along the dorsolateral 

 wall (figs. 4, 3), just in the ventral border of the frontal bone 

 (figs. 2, 1). It possibly supplies Jacobson's gland along whose 

 border it runs, but its chief distribution is to the skin on the 

 side of the head dorsal to the tentacular pit, and thence as far 

 anteriorly as the nostril. At about the level where the ventral 

 olfactory nerve leaves its canal in the ethmoid bone to disperse 

 to the olfactory epithelium, there leaves the ramus ophthalmicus 

 profundus (now designated as op. 2) a minute nerve, or two that 

 soon unite, which runs far anteriorly along the dorsal olfactory 

 epithelium (figs. 4-1, op.2h). It divides anteriorly and finally 

 disappears at the border of the olfactory epithelium, to which it 

 is evidently distributed. Near where the dorsal olfactory nerve 

 breaks up into its chief branches a branch {op.2v) is given off 

 from the ventral side of the ramus ophthalmicus profundus 

 which, for a short distance, applies itself closely to one of the 

 chief branches of the dorsal olfactory nerve, then turns abruptly 

 ventrally at the medial border of the olfactory epithelium, and 



THE JOURNAL OF MORPHOLOGY, VOL. 31, NO. 3 



