No. I.] DESMOGNATHUS FUSCA. 24 1 



Cranial Nerves. 



The size of the nerves is remarkably large, disproportionately 

 so for so small a brain and this in connection with their rather 

 blunt terminations seems to be an evidence of the persistence 

 of certain embryonic features. The following description deals 

 only with the apparent origin of the nerve roots and makes no 

 attempt to trace out the peripheral distribution. The study is 

 based upon decalcified specimens verified to some extent by 

 the examination of sections. 



I. The olfactory nerve is joined by a single root to the 

 cephalo-lateral angle of the hemicerebrum, agreeing in this 

 respect more closely with the condition found by Kingsley 

 (19) in a larval Amphiii'ma rather than with that found by 

 Mrs. Gage (13) and Burckhardt (2) in Diemyctylus and Triton 

 respectively. It is a little nearer to the ventral than the 

 dorsal aspect and soon divides into a dorsal and ventral 

 branch, which again subdivides to supply the nasal capsule. 

 Jacobson's organ receives its innervation from a branch of 

 the ophthalmic. 



II. The optic nerve contains a distinct central axis of cells. 

 Mrs. Gage (13) found that in Diemyctylus there were no fibers 

 on the dorsal side of this nerve at its attachment with the 

 brain. The chiasma is not very distinct superficially, as it has 

 apparently sunk into the brain substance and protrudes very 

 slightly or not at all from the surface. 



III. The oculo-motor nerve is fairly well developed and 

 seems to arise from the usual point in the mesencephal. 



IV. The trochlearis I failed to demonstrate, though com- 

 monly present in the Amphibia; Kingsley (19) likewise failed 

 to find it in a larval Amphiwna. 



V. The trigeminus arises from the cephalo-lateral angle of 

 the oblongata. It is quite closely applied to the mesencephal 

 on each side ; at nearly the level of the caudal tip of the 

 cerebrum it leaves the cranium. In the foramen is the Gas- 

 serian ganglion. Three branches leave it, the ophthalmic, 

 maxillary, and mandibular. The former passes along the ectal 

 surface of the cranium and dorsad of the optic to the olfactory 



