CRANIAL NERVES OF CAECILIANS 509 



In Herpele and Caecilia the eye-muscles and eye-muscle nerves 

 have completely disappeared, with the exception of the rectus 

 lateralis muscle, represented by the retractor tentaculi muscle, 

 and the abducens nerve innervating the latter muscle (figs. 8-10, 

 16, rt. and VI). The sixth nerve, in its anteriorly directed course 

 after leaving the brain, comes into very close association with 

 the ganglion of the ramus ophthalmicus profundus V. In Der- 

 mophis it is difficult to distinguish the nerve from the fibers of 

 the ramus ophthalmicus profundus in the ganglion, but in Herpele 

 it is clear that there is no anastomosis between the two nerves. 

 This intimate association of the sixth nerve with the ganglion 

 of the fifth nerve is not uncommon in the amphibians. In no 

 instance has there been shown an anastomosis between the two 

 nerves. 



A compressor muscle of the orbital gland occurs in Herpele 

 and Caecilia, but is not so extensively developed as in Dermophis, 

 though the innervation is the same. The preorbital slip of the 

 temporal muscle also occurs in these forms, but its anterior at- 

 tachments are not so plainly related to the sheath of the com- 

 pressor muscle. In Herpele it appears to be attached to the 

 sheath of the muscle; in Caecilia, to the ventral trabecula. The 

 condition in Caecilia seems to be the original one: origin on the 

 trabecular region of the skull, insertion into the tendon of the 

 temporal muscle. 



Small muscles anterior to the adductor mandibulae group and 

 innervated by the ramus mandibularis V have been reported and 

 described in the Urodela. In Amphiimia and Siren (Norris, '08, 

 '13; Bruner, '14 a and b; Luther, '14) a muscle, or muscles, in- 

 nervated by the pterygoid branch of the ramus mandibularis V, 

 and having its origin on the orbitosphenoid bone in Siren and on 

 the pterygoid cartilage and maxilla in Amphiuma, is inserted on 

 the antorbital cartilage. Norris recognized two muscles in Siren 

 and Amphiuma and designated them as retractor and levator 

 of the antorbital cartilage. Bruner more correctly surmised 

 their evident respiratory function in their relation to the regula- 

 tion of the size of the choana. Luther recognized but one muscle 

 functionally and called it dilatator choanae. Luther believed 



