56 'Journal of Comparative Neurology and Psychology. 



fibers from the nucleus lateralis niesencephali (which forms the 

 colliculus), as has been stated also by Johnston for Acipenser. 

 Its decussation (represented in Fig. 1, Plate III) forms the most 

 frontal part of the so-called commissura ansulata and it is impor- 

 tant to note that it lies at the level where the union of the lobi 

 inferiores with the brain floor is still rather broad. After the 

 decussation this loop of the commissure lies directly adjacent to 

 the median line (Fig. Hi, lemniscus cruc). The first loop which 

 does not decussate lies more dorsally at the most lateral border 

 of the mid-brain. 



Now follows a second decussating group, in Lophius (Fig. 

 xxxi) going through and around the fasciculus lateralis longitudi- 

 nalis to the ventral surface, but in Gadus situated at the outer 

 border of the mid-brain. This group of fibers decussates at the 

 caudal border of the insertion of the lobi inferiores upon the brain 

 and also caudad of this point (Fig. li) and is separated from the 

 first decussation by the most caudal fiber bundles of the tr. lobo- 

 cerebellaris, which go from the lobi inferiores through both these 

 decussations of the com. ansulata into the base of the mid-brain. 

 The pars anterior of the tr. lobo-cerebellaris penetrates into the 

 base of the mid-brain in front of the first part of the commissura 

 ansulata mentioned above. 



It is peculiar that the connections of the tectum with the 

 colliculus are mentioned by most authors, but on the contrary the 

 connection of this nucleus with the lemniscus is treated of only by 

 Johnston, who besides, like C. L. Herrick, describes the nucleus 

 lateralis mesencephali as derived from the fourth layer of the 

 tectum. That a part of the lemniscus fibers end in the colliculus 

 is a fact which need not cause surprise, but which can be only an 

 additional reason for considering the rather important elevation 

 in which the nucleus lateralis is situated as the homologue of the 

 corpus quadrigeminum posterius of the higher vertebrates. A 

 part of the lemniscus ends in both, as also does the fasciculus 

 longitudinalis lateralis, which will be discussed directly. 



As appears from the second separate lemniscus decussation of 

 more medial fibers and from the fact that even in Lophius these 

 fibers first take their course medially to and through the fasciculus 

 longitudinalis lateralis (Fig. xxxi), we must consider the posterior 

 part of the com. ansulata of the bony fishes as the pars superior 

 of that commissure of the amphibians and reptiles (Edinger). 



