266 O. LARSELL 



much larger number of fine unmyelinated fibers and their term- 

 inal branches. Most of the fibers of this layer are scattered 

 without definite arrangement, but a few definite bundles are 

 present, especially in the lateral portions of the cerebellum. 

 These bundles are located posteriorly and near the layer of 

 Purkinje cells, next to be described. Only two of them could be 

 followed with any degree of certainty as to their relationship. 

 These were the dorsal portion of the cerebellar commissure and 

 the lateral cerebellar commissure (figs. 5, 6, and 15, com.cb., 

 com.cb.L). The few cells present in this layer (fig. 7) are irreg- 

 ularly scattered and of medium size. They are multipolar, but 

 so far as the preparations available indicate, bear no resemblance 

 to the basket cells of the corresponding layer in the mammalian 

 cerebellum. There is a closer similarity to the superficial stellate 

 cells, both in the arrangement of their processes and in the posi- 

 tion of the cells near the surface of the molecular layer. 



The layer of Purkinje cells is represented in Amblystoma by 

 cells of relatively large size. They are arranged in a fairly uni- 

 form layer from one to three cells deep (fig. 4. sir. Pur.). Their 

 dendritic processes, of which from one to three or four may be 

 counted, extend outward into the molecular layer. The branch- 

 ing of these processes is very simple and limited. As revealed 

 by Golgi preparations (figs. 8, 9, 10, and 11), each of the primary 

 dendrites may give off two or three secondary branches, and these 

 in turn may ramify, but beyond this no divisions were observed. 

 In some of the preparations gemmules are present on the secon- 

 dary and tertiary branches. The primary branches are dis- 

 tributed both horizontally and dorsoventrally, i.e., their distri- 

 bution is not confined to a narrow zone of relatively wide area, 

 but rather they radiate in such a manner as to outline roughly 

 a pyramid, with the cell body at its apex. The Purkinje cells of 

 this layer are especially numerous in the lateral portions of the 

 cerebellum (corpora cerebelli). Some of their processes from this 

 region extend forward and laterally toward the tectum of the 

 midbrain, and some of the smaller branches appear to enter the 

 tectum (figs. 10 and 11). 



