288 THE BRAIN OF THE TIGER SALAMANDER 



Tractus tegmento-isthmialis (p. 283 and fig. 21).— These fibers from 

 the dorsal to the isthmic tegmentum form a large part of the dorsal 

 tegmental fascicles of group (7), but many of them are mingled with 

 more dispersed fibers of tr, tecto-tegmentalis. 



Tractus tecto-tegmentalis (fig. 21).— Fibers from all parts of the 

 superior and inferior colliculus stream backward into the isthmic 

 tegmentum. Most of the former enter dorsal tegmental fascicles of 

 group (7) in company with longer fibers of tr. tecto-bulbaris rectus 

 (p. 225), but many of them descend dispersed in the neuropil (fig. 79). 



Tractus pedunculo-tegmentalis crticiatus.— These, as described 

 above (p. 278), enter the ventral median tegmental fascicles of group 

 (1) from the peduncle and, after decussation here, pass to the isthmic 

 tegmentum by way of f . tegmentalis profundus. 



Tractus 7namillo-tegmentalis .—^ome fibers from the dorsal hy- 

 pothalamus reach the isthmic tegmentum accompanying the super- 

 ficial tr. mamillo-cerebellaris (p. 170). Others take a deeper course in 

 ventral tegmental fascicles of group (3) and f . tegmentalis profundus, 

 as described on page 279. 



