98 'Journal of Comparative Neurology and Psychology. 



glossopharyngeus and anterior vagus (Fig. cv), does not terminate 

 in the lobus, but immediately under it in the region of the octavus 

 itself where I could easily follow its course. 



The third nerve of the static region is that of the labyrinth, the 

 nervus octavus, commonly called nervus acusticus, a name which 

 does not suit very well, as this surely has much more vestibularis 

 fibers than acusticus fibers, which, however, for the teleosts at 

 least, are very probable from Parker's researches in this matter. 



The octavus terminates in part in a nucleus at the place of its 

 entrance, situated dorso-laterally in the oblongata under the cere- 

 bellar crest, as has already been described by Edinger and 

 Haller. In my fish, however, a small part ends in larger cells 

 which are more ventrally situated, as also mentioned by Haller, 

 of which rarely more than two or three are found in any one 

 section (Fig. civ). I do not venture to say with certainty whether 

 we may see in this nucleus the homologue of the more ventral 

 nucleus which Gaupp described in the reptiles, which might have 

 an auditory character. It is mentioned neither by Van Gehuch- 

 TEN for the teleosts nor by Johnston for the ganoids. 



But the greater part of the fibers terminate in other regions. 

 One part goes straight on into the cerebellum, as Edinger 

 showed experimentally and as Johnston stated for other fishes, 

 while a much larger part runs caudad on the dorso-lateral border 

 of the oblongata and may be followed, decreasing in circum- 

 ference, nearly to the nucleus Rolaiidi. That there are any fibers 

 entering Rolando's nucleus itself, as Johnston maintains for 

 Acipenser, I think not probable, even in the selachians, as this 

 name is intended for the region where the tr. descendens N. quinti 

 begins to terminate and which in carmin preparations is distin- 

 guished by a somewhat darker color. The terminal region of the 

 fibers of the octavus, however, passes so gradually into the ter- 

 minal region of the descending fifth tract and lies so near to it 

 that the whole matter is one of individual judgment. It is, how- 

 ever, certain that the fibers of the octavus are reduced to a mini- 

 mum by the time the descending trigeminus has reached the 

 nucleus Rolandi (Figs, cvi, cvii). 



From all this it appears very distinctly both in Galeus and in 

 Angelus squatina that both the nucleus Rolandi and the static 

 region are continuations of the dorsal sensory field of the medulla 

 spinalis and are everywhere sharply contrasted to the communis 



