THE CEREBELLUM OF AMBLYSTOMA 261 



laterally by the auricular lobe, so that it forms in reality a con- 

 tinuation of the IV ventricle into the auricular lobe. The re- 

 cessus lateralis is also covered, in adult Amblystoma, by massive 

 tissue on all sides except caudodorsally, where the membranous 

 chorioid plexus forms its roof. This is in contrast to the con- 

 dition present in larval Amblystoma, in which the covering of 

 the lateral recess is almost entirely membranous. 



Laterally the main mass of the cerebellum is continuous with 

 the auricular lobe and the rhomboidal lip of the medulla oblon- 

 gata (figs. 1, 2, and 3). As pointed out by Herrick ('14) for uro- 

 deles in general, the relation of the cerebellum to the rhomboidal 

 lip is very similar to that found in early embryonic stages of 

 mammals. In Amblystoma there is relatively more massive 

 structure than in lower forms of urodeles. The auricular lobe is 

 closely related to the corpus cerebelli rostrally and dorsally. 

 Johnston ('06), in summarizing the vertebrate cerebellum, states: 

 "In most vertebrates the lateral walls bulge outward and for- 

 ward as the auricular lobes, the floccular lobes in man." This 

 describes the relation of the auricular lobe to the rest of the cere- 

 bellum in Amblystoma, with the reservation that, the bulging is 

 quite limited. 



Herrick has defined the corpus cerebelli in Necturus as the 

 cerebellar tissue which forms the anterior wall of the lateral re- 

 cess and corresponds to the chief mass of the cerebellum in higher 

 Amphibia and Reptilia, and the eminentia ventralis cerebelli as a 

 forward extension of the eminentia trigemini which is continuous, 

 in front of the lateral recess, with the corpus cerebelli. In Ambly- 

 stoma there is apparent a pronounced eminence which projects 

 posteriorly and downward into the ventricle, in the region corre- 

 sponding to the corpus cerebelli of Necturus. This eminence 

 (which represents only a part of the body of the cerebellum as 

 Herrick used this term) is located medially of the anterior di- 

 verticulum (fig. 3, cxb.). It is continouus with the eminentia 

 cerebellaris ventralis, which in Amblystoma extends laterally and 

 upward in such a manner as to form the principal part of the 

 anterior wall of the lateral recess. As compared with Necturus, 

 this entire region of the brain of Amblystoma appears telescoped 



THE JOURNAL OF COMPARATIVE NEUROLOOY. VOL. 31, NO. i 



