272 O. LARSELL 



processes terminate in short twigs which resemble the claw-like 

 telodendrites of the granule cells of more highly developed cere- 

 bella (figs. 7 to 14). In only a few instances was an axone ob- 

 served to pass from such cells (figs. 11 and 14). When present it 

 is directed toward the molecular layer, but becomes lost among 

 the numerous fibers of fine caliber there present. No certain in- 

 dication of bifurcation within the molecular zone was noted. 



The fibers of the granular layer appear to be all myelinated, 

 except for the terminal branches which end within it. A well- 

 marked bundle of myelinated fibers passes through the layer from 

 one side of the cerebellum to the other. This includes the cere- 

 bellar commissure and, for part of its course, the tractus spino- 

 cerebellaris ventralis, although the latter is independent through- 

 out much of its course within the cerebellum (fig. 16, tr.sp.cb.v.). 

 Fibers from this large bundle are given off at short, irregular 

 intervals and terminate among the cells of the granular layer. 

 Some of these fibers (figs. 7 and 14, m.fi.) appear to be related 

 to the moss fibers of the more highly developed cerebellum. In 

 Golgi preparations they are seen to terminate in short, stout 

 twigs, and along their course, especially at the points of branch- 

 ing, are found the nodosities characteristic of moss fibers. Other 

 terminations within the granular layer consist of long slender 

 processes (fig. 15, t.f.) with fine varicosities here and there along 

 their course, but without the stout terminal twigs just noted. 

 These appear to come from the tractus spinocerebellaris ventralis, 

 but this was not determined with certainty. According to Ramon 

 y Cajal, the moss fibers in mammals are the terminal arborizations 

 of afferent fibers which enter the cerebellum through the inferior 

 peduncle, while the climbing fibers, which the last described 

 type of ending most closely resembles, enter from the brachium 

 pontis. It is difficult to apply this statement to the cerebellum 

 of Amblystoma, as the brachium pontis is altogether lacking. 

 The moss fibers may be the terminal arborizations of the tractus 

 spinocerebellaris dorsalis, thus passing into the cerebellum 

 through the region which in the more differentiated cerebellum 

 is the inferior peduncle. If the second type described are term- 

 inal fibers of the tractus spinocerebellaris ventralis, as they ap- 



