V. KuPFFER, Cranial Nerves of Vertebrates. 331 



commissure, described by Ahlborn, between the first tri- 

 geminus ganglion (Gn. ophthalmicum) and the facialis gan- 

 glion (v. Fig. 11) has also been derived from the epibranchial 

 cord, and the latter has consequently divided as it proceeds 

 cephalad, cannot be finally answered now, with probability, 

 either way. But I must call attention to the fact that I did 

 not see direct commissures between the principal ganglia, so 

 that there is a certain warrant, pending further disclosures, 

 in deriving all commissures in general between the vagus and 

 trigeminus regions from the epibranchial cord. 



DESCRIPTION OF PLATE XXII. 



Fig. 1. It, neural cord: z, 'twixt cord (Zwischenstrang). ^^ . 



Fig. 2. //, neural cord; d P, dorsal brain-plate. ^5°. 



Fig. 3. h, fore brain; a, rudiment of eye; d P, dorsal brain-plate; 

 11, rudiment of nerve; g, ganglion, ^oo 



Fig. 4. //, mid brain; /, root-border; jn, mesoderm; r//, chorda, 

 d, gut; g/, lateral ganglion, ge, epibranchial ganglion, ^oo 



Fig. 5. //, mid brain; ch, chorda; d, gut; 711, mesoderm; /, root- 

 border; Jis, dorsal spinal nerve; nb, branchial nerve; gl, lateral ganglion; 

 gvi, medial ganglion. 



Fig. C. //, hind .brain; /, root border; 11 s, dorsal spinal nerve; nb, 

 branchial nerve; gl, lateral ganglion of vagus; ge, epibranchial ganglion; 

 ^.T, sjmpathic ganglion; ;/rf, neurodermis. 200 



Fig. 6. h, hind brain; ch, chorda; d, gut; ;«, mesoderm; ns, dorsal 

 spinal nerve; nb, branchial spinal nerve; gl, hind end of lateral ganglion 

 of vagus; ge, epibranchial ganglion; nd, neurodermis. 



Fig. 7. h, fore brain; gin, medial ganglion; gl, lateral ganglion, 

 both belonging to the I principal ganglion of the trigeminus; ge, epi- 

 branchial ganglion; ;;.?, dorsal spinal nerve; ;/f/, neurodermis. *J°. 



Fig. 8. Branchial nervous system of an Ammocoetes 4 mm. long, 

 projected on the median plane, about ^J^. A, eye; N, nose; O, ear; 

 /, first, //, second principal ganglion of the trigeminus; ///, principal 

 ganglion of facial; /I', principal ganglion of glosso-pharyngeus, fusing 

 ventrally with the sixth epibranchial ganglion; V, principal ganglion of 

 vagus, first, seventh and twelfth epibranchial ganglia; K^-K^, gill 

 pouches; ch, chorda; /, nervus lateralis. Going out from the epi- 

 branchial ganglia and proceeding ventrally between the gill pouches are 

 the terminal branches of the branchial nerves, forking into the ramus 

 posttrematicus and pra?trematicus. The rr. prsetrematici end in the 

 structure with a knob, the ganglion praetrematicum, about half way up 

 the gill pouch. The foremost of these ganglia is before the stomodseum, 

 on a twig of the maxillaris. The small circles behind the second to the 



