16 C. JUDSON HERRICK 



(corpus cerebelli), because it seems to be the direct precursor of 

 the chief cerebellar mass of higher amphibians and reptiles. The 

 cerebellar tissue in the floor of the lateral recess (eminentia ven- 

 tralis cerebelli) gives rise to the greater part of the feebly devel- 

 oped brachium conjunctivum and is therefore probably the 

 primordium of the roof nuclei and the nucleus dentatus of the 

 mammalian cerebellum. 



The corpora cerebelli of the two sides are connected dorsally by 

 a strong commissural system. In Necturus and Amphiuma the 

 grey matter of the cerebellum does not reach the mid-dorsal plane 

 except for a few cells of doubtful significance associated with the 

 cerebellar commissure. In Cryptobranchus there is a thin bridge 

 of grey matter extending across the mid-dorsal plane, which in 

 higher urodeles like Amblystoma becomes massive. 



The fiber connections of the cerebellum of Necturus are essen- 

 tially similar to those of the area acustico-lateralis father back in 

 the rhomboidal lip, save for the presence of the dorsal cerebellar 

 commissure and the absence of demonstrated root fibers of the 

 cranial nerves. Fibers of the VIII and lateral line nerves termi- 

 nate freely throughout the area acustico-lateralis, but no medul- 

 lated fibers of these systems reach the body of the cerebellum in 

 this species. Unmedullated correlation fibers, and possibly un- 

 medullated root fibers, pass between the area acustico-lateralis 

 and the cerebellum. The body of the cerebellum receives strong 

 medullated tracts from the spinal cord and oblongata and from 

 the tectum mesencephali, also an unmedullated tract from the 

 hypothalamus (tractus mammillo-cerebellaris) . There are two 

 spino-cerebellar tracts, a dorsal and a ventral. The dorsal tract 

 ends chiefly in the body of the cerebellum of the same side; the 

 ventral tract ends partly uncrossed, but most of its fibers enter the 

 cerebellar commissure to reach the body of the cerebellum of the 

 opposite side. These tracts probably also carry ascending fibers 

 from the sensory nuclei of the oblongata to the cerebellum of the 

 same and the opposite side. 



The efferent tracts from the cerebellum, so far as demonstrated 

 in Necturus, decussate in the ventral commissure and reach the 

 tegmentum of the opposite side of the medulla oblongata and 



