CRANIAL NERVES OF CAECILIANS 545 



According to Marcus, there are four lateral-line nerves in the 

 trunk of the larva; one dorsal, two medial, and one ventral. 

 They are completely absent in the adult. As will be seen later, 

 the ramus lateralis profundus of Marcus is a motor branch of a 

 spinal nerve. In the late larva of Ichthyophis there is a single 

 lateral-line nerve supplying a dorsal series of neuromasts (figs. 

 35, 43, X lat.). The occurrence of a trunk ganglion on the vagus 

 nerve introduces a feature entirely foreign to the Urodela and 

 Anura. Willard ('15) reports the occurrence of a trunk gan- 

 glion on the tenth nerve in Anolis, and an absence of a dorsal 

 cutaneous branch. Only two pairs of distinct branchial nerves 

 are represented in the adult caecilians, a condition not unexpected 

 considering the rudimentary condition of the branchial arches. 



THE OCCIPITAL NERVE 



A distinct nerve between the vagus and the hypoglossal nerves 

 is uncommon in the Urodela and Anura. Ftirbringer ('97) finds 

 an occipital nerve in Cryptobranchus japonicus. Druner (1901, 

 1904) reports the same in C. alleghaniensis and indications of 

 it in Salamandra and Triton. Wiedersheim ('79) figures, in 

 Siphonops, a dorsal branch of the vagus nerve, which is doubt- 

 less the occipital. Marcus ('10) describes an occipital nerve in 

 the larva of Hypogeophis. 



In Herpele the occipital nerve arises from the ventrolateral 

 border of the nem-al tube near the border-line between brain 

 and spinal cord. It passes anteriorly until the anterior border 

 of the first vertebra is reached, where it turns abruptly latero- 

 ventrally and then posteriorly around the anterior border of the 

 vertebra and the occipital condyle, in the space between the 

 latter and the posterior wall of the ear capsule (figs. 32, 33, ocn.). 

 The nerve runs out parallel with the IX-X roots, but separated 

 from them by a blood-vessel, and passes across and through the 

 posterior border of the vagus root ganglion in such a way as to 

 give the appearance of being a part of the ninth-tenth complex. 

 Leaving the root ganglion, it gives a small twig to the anterior 

 part of the rectus sub vert ebralis muscle and then passes into 

 the dorsal trunk musculature, anastomosing with a dorsal 

 branch of the first spinal nerve. 



