12 C. JUDSON HERRICK 



pass very close to the caudal end of the mesencephalic V nucleus 

 and all of them may easily reach these cells. Sections stained for 

 medullated fibers only are quite inadequate to resolve this point, 

 for the cells referred to lie so close to the cerebellar commissure 

 that fibers destined to reach these cells from the commissural 

 tract might lose their medullary sheaths before leaving the com- 

 missural tract. 



Hirsch-Tabor ('08, p. 727) and later Bindewald ('11) describe 

 in Proteus a 'commissura intertrigemina' which is regarded by the 

 latter author in Proteus, Hypogeophis and Cryptobranchus as a 

 true commissure between the sensory trigeminal nuclei of the 

 oblongata. This seems to include the entire cerebellar commis- 

 sure of the present account, which I have found to be a much 

 more complex structure in Necturus, Amphiuma and Crypto- 

 branchus. Bindewald recognizes other elements than the trigem- 

 inal fibers in Cryptobranchus and to the present writer it seems 

 probable that a renewed examination of the brain of Proteus will 

 reveal other components of the commissure there also. Some 

 fibers of my tractus spino-cerebellaris ventralis et dorsalis (es- 

 pecially the more dorsal system) probably come from the 

 primary sensory trigeminal nucleus of the same side and are to be 

 regarded as secondary trigemino-cerebellar fibers. Some of these 

 fibers enter the cerebellar commissure, but even these fibers could 

 not properly be described as a 'commissura intertrigemina,' for 

 their terminus is probably the cerebellum rather than the trigemi- 

 nal nucleus of the opposite side. The same conditions probably 

 prevail in Proteus, for one of Hirsch-Tabor's figures ('08, p. 726, 

 fig. 2) shows that this animal possesses grey matter in the wall of 

 the anterior diverticulum of the recessus lateralis which corre- 

 sponds in position and other relations so far as shown to the corpus 

 cerebelli of my description. In larval Amblystoma I find a large 

 sensory root of the trigeminus which ascends to end in the eminen- 

 tia trigemini, and some fibers of this tract continue forward as a 

 separate bundle accompanying the tractus spino-cerebellaris to the 

 rostral end of the auricular lobe. 



