Kappers, Teleostean and Selachian Brain. 5 1 



commissure of the ganglia sacci vase, mentioned above and 

 evidently is the same as the one referred to in Scyllium by Haller 

 as a connection of the two lateral cell regions of the lobi inferiores. 

 In my opinion it is homologous with the postinfundibular com- 

 missure which I described in Gadus and which is also a bilateral 

 connection of the two lateral regions of the lobus. 



It now remains only to treat of the tr. loho-ccrehellaris, or tr. 

 tegmento-cerebellaris, which has already been mentioned several 

 times. The fibers of this tract which originate farthest caudally 

 gather in the most distal part of the lobi from the extensive cellular 

 layer which surrounds its ventricle (Figs. Ixv and Ixvi). After 

 having curved slightly forward, the fibers again turn backward 

 in the base of the mid-brain. These relations are similar to those 

 in Gadus, though in Galeus the lobi infundibuli protrude somewhat 

 farther backward than in Gadus, so that more of the fibers have 

 to make the curve forward before turning backward. In both 

 Galeus and Gadus this nucleus is very extensive and is dark in 

 color, due, it seems to me, not only to the abundance of small 

 medullated fibers, but also to a slight pigmentation. 



The lobo-cerebellar fibers gather in small bundles which form 

 almost the whole base of the posterior hypothalamus region. 

 Medially they border on the thalamo-spinalis fibers, and, farther 

 back in the mid-brain, on the tecto-spinalis fibers which are situ- 

 ated partly above them and partly run along their lateral side. 

 After their decussation, which takes place along with the com- 

 missura ansulata near the origin of the oculomotorius, the fibers 

 disappear in the anterior part of the cerebellum. 



Accordingly, we find in the lobi inferiores of the selachians the 

 main features in the same relation as in the teleosts. In both the 

 tr. strio-thalamicus ends without decussation in the higher layers 

 of this region. In both the tr. lobo-cerebellaris arises in the 

 posterior half and the tr. sacci vasculosi in the ventral half. In 

 both a comparatively poorly developed commissure is found be- 

 tween the nuclei of origin of both of the tracts mentioned, the com. 

 postinfundibularis superior. In both the tr. thalamo-lobaris ends 

 in the more frontal part of the lobus. The 'tween-mid-brain 

 connection, described as tr. mesencephalo-lobaris posterior in 

 the teleosts, is most probably to be found in the selachians also, 

 although it is difficult to follow it among the very numerous fibers 

 of this region. 



