THE CEREBELLUM OF AMBLYSTOMA 279 



tion of the cerebellum. The cells of origin appear to lie in the 

 pars dorsalis hypothalami. The fibers pass from this region 

 dorsocaudad and toward the midplane. After passing dorsal to 

 the region of the interpeduncular nucleus, they dip ventrally be- 

 hind this nucleus, then assume a more dorsal course and pass 

 through the midbrain into the tegmentum and the cerebellum. 

 Within the cerebellum (figs. 11 and 13, tr.m.cb.) they are scattered 

 loosely in the dorsolateral region, and show characteristic vari- 

 cosities. They appear to come into relation with dendritic pro- 

 cesses of the larger Purkinje cells (fig. 11) above described, which 

 extend toward the midbrain. These fibers correspond to the 

 tractus mammillocerebellaris which appears to be present in 

 Necturus also. From the interpeduncular region, in Amblys- 

 toma, a number of fibers accompanies the mammillocerebellar 

 tract in its course toward the cerebellum, lying ventral and par- 

 allel to it. The fibers appear to have their origin from cells in 

 in the interpeduncular nucleus. They pass dorsally and caudad 

 into the tectum mesencephali, where many of them appear to 

 end. Others, however, appear to continue caudad into the 

 cerebellum in company with those of the tractus mammillo- 

 cerebellaris. This appearance was chiefly due to the greater 

 numbers of fibers in the region of the cerebellum occupied by 

 the tractus mammillocerebellaris, as compared with the num- 

 ber constituting this tract rostrad of the nucleus interpeduncu- 

 laris. The number within the cerebellum appears to correspond 

 more closely with that of the combined tracts in their course 

 between the interpeduncular region and the mesencephalon, bub 

 this greater number within the cerebellum may be due to pro- 

 fuse terminal branching of the mammillocerebellar fibers. This 

 point could not be determined in the material available. It is 

 possible that some are fibers of the secondary gustatory tract 

 which pass through the lateral region of the cerebellum. Her- 

 rick ('17) believes that the mammillocerebellar tract which he 

 had previously tentatively established in his description of the 

 cerebellum of Necturus "includes the combined secondary and 

 tertiary visceral tract, with perhaps mammillotegmental fibers 

 mingled with them." In the Golgi preparations of Amblystoma, 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 31, NO 4 



