No. 1.] AMPHIBIAN BRAIN STUDIES. 73 
sal and ventral nuclei are composed respectively 
of unmistakable sensory and motor cells. While 
one of the lateral or intermediate nuclei is composed of less 
distinctively motor cells of smaller size (e.g. 9m, 7mm), the 
other (fasciculus and nucleus communis) is clearly 
sensory. 
2, The nérves of the ILL—1Vi=V. E pairs: forma 
special system with no apparent homology or con- 
nection with the motor elements of the Vagus or 
Trigeminus systems. 
a7) Lhe VII. as a nerve ofespecial sense, Mas 
either no homology or an incomplete homology in 
the arrangement of its sensory nuclei and tracts 
with the sensory elements of the Vagus and Tri- 
geminus systems. 
If the fasciculus communis is found to enter the 8th 
instead of the 7th, this section must be modified to an incom- 
plete homology. 
I do not consider that these observations are sufficiently well 
tested to give sure support to theoretical deductions as to the 
homologies of the cranial and spinal nerve elements. It is 
clear that the Vagus and Trigeminus systems approach nearest 
the typical spinal nerve arrangement, and the apparent presence 
of two sets of sensory and two sets of motor nuclei in these 
systems is of great interest in its bearing upon Gaskell’s theory 
of the compound nature, somatic and splanchnic, of the anterior 
and posterior roots. As frequently stated above, the motor or 
sensory character of some of the nuclei and tracts can only be 
determined by the study of their peripheral distribution, since 
the character and position of the cells themselves, as shown in 
the pale ganglion cells of the 8th and the small cells of the 
lower nucleus of the 7th, is an uncertain guide as to the nature 
of the fibres which spring from them. Even with this precau- 
tion it is a great advance to determine the presence of these 
two sets of nuclei for each of these systems. 
Ill. THE ENCEPHALON. 
THE CEREBELLUM. 
As already observed, the cerebellum in the Uvodela is 
widely different from that in the Azura in its size and internal 
