182 PROCEEDINGS OF THE AMERICAN ACADEMY. 



serian ganglion, as it does in some of the Amphibia, but (Fig. 3) comes 

 into contact with the ventral side of r. ophthalmicus V. {V. opt.) a short 

 distance anterior to its emergence from the ganglion. Owing to this 

 condition it is much easier to follow the fibres of the two nerves in 

 this species than in those where the two nerves emerge from the gan- 

 glion together. Herrick ('94, p. 200) describes for Amblystoma two 

 branches of the sixth nerve, one of which goes to m. rectus exteruus, 

 the other to m. retractor bulbi, but he thinks the branch to the latter 

 muscle ought really to be assigned to the trigeminus, and so colors it in 

 his figures. Although iu Spelerpes the sixth lies in immediate contact 

 with r. ophthalmicus V., yet I was able to trace its fibres with accuracy 

 in several series of preparations, and am certain that there is no ventral 

 branch given off" from V., but that VI. divides into two branches, one 

 ( VI. rt. ex.) going to m. rectus externus, the other ( VI. ret. bl.) to m. 

 retractor bulbi. On the latter branch was found, in the region indicated 

 by cl.gn' . (PI. 2, Figs. 3, 4), a distinct aggregation of ganglionic cells, 

 similar to those enveloping the oculomotorius. I have found no refer- 

 ence to such cells connected with the sixth nerve, except in one sentence 

 of Strong's article ('95, p. 134), where he says: "There seem to be 

 ganglion cells in connection with it [abducens] (703), although these 

 may belong to the oculomotor nerve." I have not yet tried methods 

 to show the connection of these ganglionic cells with the nerve fibres. 

 Only two roots were found, as in Necturus ; these emerge from the 

 ventral side of the medulla in about the same transverse plane as the 

 most anterior roots of IX. + X. 



D. Trigeminus. 



(1) Roots. — The little study which I have hitherto given to the roots 

 of the cranial nerves in Spelerpes has shown that there is apparently 

 a close correspondence to the condition found by Kingsbury ('95.) in 

 Necturus. 



Fibres forming the trigeminus root are: (1) a large ascending bundle 

 (Plate 1, Fig. 2, V. rx.) of mostly small fibres lying ventrad to the 

 eighth nerve, presumably the ascending tract of the fifth, though they 

 were not traced back into the dorsal column of the spinal cord. It is 

 possible that fibres from a sensory nidus (terminal) may be associated 

 with these, as in Necturus; but none were distinguished; (2) two small, 

 presumably motor, bundles of large, deeply staining fibres ( V.rx.mot.), 

 which arise from the floor of the metencephalon and join the ventral 

 side of the ascending tract of the fifth, just before its exit from the brain ; 



