248 C. JUDSON HERRICK 



In the frag (Gaupp, '99, p. 50) there is a large and very dense 

 nucleus behind the tectum at the level of the decussation of 

 the IV nerves, which is termed the 'ganglion isthmi.' Since 

 the term ganglion should be reserved in vertebrate neurology 

 for collections of nerve cells outside the central nervous system, 

 I shall term this structure the nucleus isthmi. The nucleus 

 posterior tecti of Necturus may represent the nucleus isthmi 

 in a far less compact and integrated form than in the frog, 

 though in the present state of our knowledge this homology 

 should not be accepted without reserve. Bellonci ('88, p. 26) 

 regards the nucleus isthmi of the frog (which is the nucleus 

 magnus of Reissner, '64) as the true corpus posterius, or collicu- 

 lus inferior — an untenable homology, as has been pointed out by 

 Gaupp ('99, p. 62). 



6. The visceral lemniscus 



In larval Amblystoma I described ('14 a, p. 373) an uncrossed 

 secondary visceral tract comparable with the secondary vagus 

 bundle of Mayser ('81) and with my ascending secondary gusta- 

 tory tract ('05) in teleosts. Its fibers arise from neurons of 

 the nucleus of the fasciculus solitarius and terminate in an area 

 of neuropil in the isthmus region which occupies the angle be- 

 tween the auricular, lobe and the midbrain ('14 a, fig. 5, tr.v.a.). 

 This neuropil was regarded as the representative of the tele- 

 ostean 'Rindenknoten' of Mayser, or superior secondary gusta- 

 tory nucleus of my paper published in 1905. Associated with it 

 is a group of enlarged neurons ('14 a, fig. 52). 



The neurons which constitute the secondary visceral nucleus 

 ('Rindenknoten') can be recognized in our sections of adult 

 Necturus as a lateral extension of the central gray in the angle 

 between the body of the cerebellum and the midbrain. They 

 lie immediately dorsally of the eminentia subcerebellaris teg- 

 menti and therefore dorsally of the locus of the sulcus limitans. 

 This extension of the ventricular gray toward the surface of 

 the brain in the isthmus region must not be confused with the 

 superficial gray matter, at the rostral end of the auricular lobe 



