•246 C. JUDSON HERRICK 



As I have already mentioned in the case of Amblystoma 

 larva ('14 a, p. 376), the spino-bulbar, spino-cerebellar, spino- 

 tectal, and spino-thalamic fibers of urodeles appear to belong to 

 a single primitive ascending system which distributes nervous 

 impulses throughout the entire length of the brain stem. Many 

 of the terminals ending in all of these levels are collaterals from 

 the long tectal and thalamic fibers; this applies even to the 

 spino-cerebellar fibers, which form one of the most clearly dif- 

 ferentiated members of the system. 



4- The acoustico-lateral lemniscus , 



This is a relatively compact tract of small but heavily myeli- 

 nated fibers which arise throughout the entire extent of the acous- 

 tico-lateral area of the oblongata. It is the equivalent of the 

 fasciculus lateralis of Mayser ('81) in teleosts, and in a more 

 general sense of the lateral lemniscus of mammals. Its fibers 

 immediately after leaving their cells of origin decussate in the 

 ventral commissure of the medulla oblongata as internal arcuate 

 fibers and then turn forward in the middle depths of the stratum 

 album. In the caudal part of the oblongata this tract lies not 

 far from the rriid-ventral plane; farther forward it moves lateral- 

 ward, increasing in size, and at the isthmus turns abruptly dorsal- 

 ward to enter the tectum mesencephali. Its bulbar course in 

 Necturus has been well described and figured by Kingsbury 

 ('95, p. 192), and in the upper levels of the oblongata it is fig- 

 ured in my paper on the cerebellum ('14, figs. 4 to 11). I have 

 described the o:^igin and spinal portion of this tract in larval 

 Amblystoma under the name tractus octavo-tectalis et thalam- 

 icus ('14 a, p. 369). 



In the midbrain this lemniscus tract ascends along the ventral 

 border of the tectum through the intermediate level of the 

 stratum album (figs. 7 to 14, 21, 24, 32, 33, 35, 39, 41, 49, 53 

 to 56, 66, Im.). Most of its fibers terminate in a diffuse neuropil 

 in the more lateral and caudal parts of the tectum, i.e., in the 

 portion of the roof which I have compared with the colliculus 

 inferior of mammals (figs. 39, 53 to 56, Im.). Many terminals 



