250 C. JUDSON HERRICK 



der unmyelinated tract is seen directed forward, lateralward 

 and ventralward from the nucleus (figs. 50, 66, tr.v.t.). This 

 is the tertiary \isceral tract. It pierces the tractus bulbo- 

 tectalis to reach the ventro-lateral surface, where it joins the 

 forward extension of the secondary idsceral tract already men- 

 tioned. The combined secondary and tertiary visceral bundle 

 continues forward to the region laterally of the nucleus of the 

 III nerve. Immediately rostral to this region is the dense 

 superficial neuropil termed area lateralis tegmenti, which re- 

 ceives the supposed basal optic tract (p. 242) and the fibers of 

 the superficial tractus thalamo-peduncularis dorsalis derived 

 from the pars intercalaris thalami (p. 264). These \dsceral 

 fibers may terminate in this neuropil or they may effect other 

 connections farther rostrally (see p. 284). 



In my account of the cerebellum of Necturus ('14, p. 8) I 

 described a connection between the hypothalamus and the cere- 

 bellum which was provisionally called the tractus mamillo-cere- 

 bellaris ('14, fig. 19, tr.m.cb.) and was regarded as a special 

 portion of a diffuse hypothalamo-tegmental system. It now 

 appears that the tract there described includes the combined 

 secondary and tertiary visceral tract, with perhaps mamillo- 

 tegmental fibers mingled with them. My study of this region 

 is still incomplete. 



No commissural fibers have been traced from the secondary 

 visceral tract or its nucleus in the isthmus into the decussatio 

 veli, as in fishes, though a few fibers of this sort may occur. 



7. Tractus tecto-cerebellaris 



The connections between the cerebellum and the midbrain 

 are not condensed into definite tracts and their study is very 

 difficult. By analogy with other vertebrates it is probable, as 

 I have before suggested ('14, pp. 6, 9), that tecto-cerebellar 

 fibers are present in the confused collection of fibers bordering 

 the rostral border of the cerebellum, but I have not been able 

 to demonstrate them separately. 



