20 Journal of Comparative Neurology. 



the medulla and the greater part of it runs in the form of dense, 

 closely defined bundles into the lobus lineae lateralis (Fig. i i a). 

 As the root passes through the dorso-median nucleus several 

 small bundles branch off and end in that nucleus. A very con- 

 siderable number of these fibers do not join the main bundles 

 but enter the lateral nucleus, take the deep stain characteristic 

 of the fibers which end upon the spindle cells, run as a loose 

 bundle to the cephalic end of the acusticum and end upon the 

 spindle cells there situated. The greater number of the spindle 

 cells in this position are connected with the lateral line fibers, 

 although some fibers seem to come to them from VIII. 



The course of the spinal V tract (Figs, i, 9—13, 29, 30) 

 has been sufficiently described. A part of the fibers of the V 

 root, however, do not run in the spinal V tract. Some very 

 coarse fibers which come from the ramus ophthalmicus V run 

 in the median part of the acusticum. They are not always well 

 impregnated but in both sagittal and transverse sections they 

 are traced to the caudal end of the acusticum and some of them 

 may enter the nucleus funiculi. They are not shown in the fig- 

 ures. Other fibers of V bifurcate on entering the medulla 

 (Fig. 29), one branch going to the cerebellum, the other run- 

 ning in the spinal V tract. Still other fibers run directly to the 

 cerebellum without bifurcation. In one case a fiber which ap- 

 parently belonged to V was seen ending upon a spindle cell as 

 the VIII fibers do. 



4. The cerebellum (Figs. 2, 12, 22). 



The cerebellum consists of an inner cell layer and an outer 

 fiber layer. The cell layer is a direct continuation cephalad 

 and mesad of the two chief nuclei of the acusticum, the dorso- • 

 median nucleus taking the more important part. The fiber 

 layer consists in part of a continuation of the cerebellar crest 

 covering the outer surface of the acusticum, and in part of fibers 

 of the VIII and lateral line VII nerves. These two la}ers 

 are to be compared with the granular and molecular layers of 

 other vertebrates but it must be noted that the Purkinje cells 

 do not lie between these two layers but are scattered through 

 the inner layer. The fiber layer forms a thick dorsal commissure 



