112 Comparative Neurology. [February, 
I is connected to 2 and 3 by the upper end of the brachium 
conjunctivum, 3 to 4 by prolonged habenule, 4 to 5 by fornix, 5 
to 6 by hippocampal fibers, tractus Lancisi and gyrus fornicatus 
(the latter principally). In the case of a fish with optic lobe (2) 
developed covering the other tubercles, the course of the com- 
missures and relative mass appearance would be thus : 
Bird, as pigeon, with cerebrum developed covering I to 5, the 
optic lobe being pressed to one side. 
Qs 
The following appears to be the arrangement of the brain of 
the fox shark, with lobes equally developed. I think the main 
mass must be the optic thalamus with the quadrigeminal bodies 
fused on its surface (this latter feature ‘not represented here). 
#98 
This form appears in the mammal with equally large eee 
lobe and cerebrum. 
Evolution of the afferent longitudinal commissures, fissure of Syt- 
vius and temporal lobe-—This condition is presented by an uncon- 
voluted brain such as the beaver’s, which is but faintly fissured, 
