4 C. JUDSON HERRICK 



nize as the body of the cerebelhim and it extends backward nearly 

 as far as the VII roots. Its lateral wall is formed chiefly by the 

 anterior lobe of the area acustico-lateralis (figs. 1, 22, 23). The 

 floor of the recessus lateralis is formed in part by the eminentia 

 trigemini (em.V, figs. 1, 15,) and farther forward (figs. 2, 3, 13, 17, 

 27) by an eminence which is the direct forward extension of the 

 eminentia trigemini. This I term the eminentia ventralis cere- 

 belli (ew. cb. v.). It is directly continuous in front of the recessus 

 lateralis with the body of the cerebellum. . 



In Necturus the amount of cerebellar tissue is very small and 

 it is poorly differentiated, though there is no uncertainty regarding 

 its character. Cerebellar tissue is found on all sides of the anterior 

 diverticulum and throughout the antero-medial wall of the lateral 

 recess. The cerebellar tissue which forms the anterior wall of the 

 lateral recess is not extensive; but since the chief mass of the 

 cerebellum in higher Amphibia and Reptilia seems to be devel- 

 oped in this region, it will be termed the body of the cerebellum 

 (coi-pus cerebelli — c.cb., figs. 7, 8, 14, 15, 17 to 23, 27). 



The body of the cerebellum is a bilateral structure whose two 

 chief masses are connected across the mid-dorsal plane by the 

 cerebellar commissure (with which are associated decussating 

 fibers of the IV nerve and fibers of the mesencephalic root of the 

 V nerve the whole forming the so-called decussatio veli). In 

 gross preparations there is no evidence of any other massive tissue 

 in the mid-dorsal plane of the cerebellum, but sections show (fig. 

 25) under the fiber bundles a few nuclei, in addition to those of the 

 ependyma, which may be of nervous character. 



The cerebellar commissure is bounded rostrall}^ by the tectum 

 mesencephali, whose roof at this point is veiy thin, though mas- 

 sive, thus forming a frenulum veli medullaris anterioris. This 

 forms the roof of a dorsal dilation of the mesencephalic ventricle, 

 which I term the recessus posterior mesencephali (r.pjn., fig. 25). 

 The frenulum contains a collection of cells of the nucleus mes- 

 encephalicus trigemini arranged in a thin layer. These are always 

 present laterally of the meson, but in the medial plane they may 

 be absent. Even in the latter case the roof membrane is not a 

 simple epithelium, but contains two or three rows of nuclei. 



