Kappers, Teleostean and Selachian Brain. 37 



curve runs under the fibers of the commissura posterior and then, 

 accompanying the fasciculus retroflexus for some distance, goes 

 downward medially of the tr. strio-thalamicus, then bends again 

 laterally without crossing ending in the lobes above the ventricles. 



(2) The second connection of this kind arises in the nucleus 

 corticalis and nucleus prcerotundus (between which the terminal 

 loops of the commissura transversa run) and goes downward 

 (Fig. xliv) in the same way but more nearly in a single vertical 

 plane than the first tract, mesad of the tr. strio-thalamicus, to end 

 in the central part of the lobus inferior where the tr. olfacto- 

 lobaris medialis (or tr. olfacto-hypothalamicus medialis) also ends 

 (Fig. xlv). I have called this the tractus mesencephalo-loharis 

 anterior. 



(3) The third connection of the hypothalamus with regions 

 situated more dorsally is formed by the tr. rotundo-lentiformis, 

 which I have named after the nuclei which are connected by it. 

 This tract leaves the nucleus rotundus proprius together with the 

 fibers of the commissura horizontalis and accompanies the fibers 

 of this commissura to the region directly behind the commissura 

 posterior. Perhaps the same tract has been seen by Catois, who 

 considered it to be the same as the dorso-laterale-ventrale Zwis- 

 chenhirnbahn of Haller, who saw a similar connection. Catois 

 describes this tract as originating "en arriere de la commissure 

 blanche posterieure," but his opinion was that its fibers also go 

 into the commissura inferior. The latter, I think, were the fibers 

 of the horizontal commissure which accompany this tract, which is 

 also accompanied by a large tract originating behind the com- 

 missura posterior and going to the cerebellum. 



(4) To this gr6up of shorter connections belongs the tractus 

 mesenccphalo-loharis posterior, consisting of a series of heavily 

 medullated fibers which connect the back part of the lobi with the 

 region of the nucleus lateralis mesencephali and the adjacent 

 tectum along the exterior side of the brain. The strong develop- 

 ment of this tract is correlated with the importance of the regions 

 connected by it (Figs, xlvii, xlviii). 



The fourth group of fibers consist of short but large strongly 

 medullated bundles, part of which probably pass caudad into the 

 tractus mesencephalo-lobaris posterior, while the greater part 

 constitute : 



(i) Fasciculus intralobaris. This connects the most anterior 



