146 Journal of Comparative"_Neurology. 



lobes as a single root, agreeing in this respect with Desmogna- 

 thus and AmpJiiuma rather than Cryptobranchiis, Dicmyciylus and 

 Triton in which two roots have been found to exist by Wilder 

 ('89), Mrs. Gage ('93 ) and Burckhardt ('91 ) respectively. The 

 nerves are quite long, dividing soon into numerous branches 

 which are distributed to the olfactory capsules. In the larva 

 these nerves are short, the fibers being given off laterad direct- 

 ly to the olfactory capsule which closely adjoins the brain. 



II. The rudimentary condition of the eyes in Necturiis is 

 naturally ' accompanied by a similar condition of the optic 

 nerves. The primitive lumen of the optic vesicle is persistent 

 and the nerves are hollow for a considerable distance periphe- 

 rad. This fact has been already mentioned byOsborn('88) 

 and Herrick ('93, 2). Furthermore, the optic fibers in Ncctiirus 

 are entirely amyelinic, at least in their course in the optic tracts 

 and the central portion of the optic nerve. This was ascer- 

 tained both from Weigert and osmic acid preparations. The 

 specimens were fully mature adults measuring over 30 centimet- 

 ers in length. This condition in Necturus is not, however, 

 unique ; Edinger ('92 ) found that in young frogs and in 

 young adult Tritons and Salamanders the optic fibers were 

 almost entirely amyelinic. 



III. The oculomotor nerve takes its origin at the usual 

 point in the floor of the mesencephal. Though small it was 

 always readily found. 



IV. The trochlearis could always be easily detected, but I 

 was unable to trace it to its exit from the cranium. A large 

 number of its fibers immediately after its decussation were 

 distibuted to the metaplexus. It is possible that such fibers 

 represent a sensory contingent of the 4th nerve. Gegenbaur 

 ('70) has stated that the fourth nerve contains sensory fibers in 

 selachians and Amphibia. Strong ('90) likewise, found in the 

 tadpole a sensory intracranial branch. No ganglion was 

 observed, however, in Nectwus though numerous cells occurred 

 among the fibers of this nerve. 



V. The trigeminus is of good size in Nectnnis. It arises 

 in the usual place in Amphibia and passes latero-cephalad to 



