Kappers, Teleostean and Selachian Brain. 95 



as the enormous quantity of fibers of the oblongata and corpora 

 restiformia is so great that even the very best preparations cannot 

 give anything Hke certainty in this matter. 



Now, before going on w^ith the nerves I must mention an impor- 

 tant cerebellar connection which is found in the same place in 

 plagiostomes and teleosts, the tr. cerebello-spinalis ventrahs, which 

 originates from the cerebellum and leaves it by the auriculus 

 behind the trigeminus and in front of the facialis, descending 

 along the lateral wall of the oblongata (Fig. ci), taking such a 

 course that it lies close to the mesial side of the nervus octavus 

 where it enters the oblongata (Fig. civ). Then it approaches 

 closer to the raphe, through which it sends some fibers which, 

 however, cannot be followed to their termination without experi- 

 mental examination. Under this name Edinger described a 

 tract in Scyllium which leaves the cerebellum through the decus- 

 satio veli and which he could follow only to the trigeminus region. 

 But I have given the same name to the tract which I have described 

 by reason of its likeness in both origin and course through the 

 oblongata to the tract described under this name in the teleosts. 



The nervus abducens, consisting of motor fibers only, leaves the 

 oblongata behind the facialis as in the bony fishes. Its nucleus 

 lies laterally of the deeper fibers of the dorsal longitudinal bundle 

 and consists of rather large polygonal cells which extend some- 

 what farther dorsally in Galeus than in Gadus, where they really 

 lie in the lower third of the oblongata. But in this respect both 

 the selachians and the teleosts show an important difference 

 from the higher vertebrates, where this nucleus lies very close 

 under the ventricle. That a part of its fibers decussate through 

 the fasciculus dorsalis, though more clearly apparent in Gadus, 

 is also observable in Galeus (Fig. civ). As I have already ob- 

 served, in Weigert preparations of selachians no separate tectal 

 tract can be followed into the nucleus of the abducens. The 

 enormous mass of fibers prevents such an observation. 



The nervus facialis, leaving the medulla in almost the same 

 place as the octavus, constitutes the most frontal group of fibers 

 of the acustico-facialis complex. It is a mixed nerve, of which 

 the sensory part is intimately related to that of the ninth nerve, 

 as the situation of its terminal nucleus, near the glossopharyngeus 

 and in intimate relation with it, falls in the most anterior part of 

 the communis region. In Figs, cii and ciii its mode of entrance is 



