THE AMYGDALA IN AMPHIBIA 243 
distance farther caudad. The four quadrants into which the 
remainder of the hemisphere is divided in Anura can be recognized 
in Urodela; the two medial quadrants are structurally very 
distinct, but the two lateral are incompletely separated. The 
lateral forebrain bundle is the chief distinguishing character of 
the ventrolateral area and the dorsolateral olfactory tract of the 
‘dorsolateral area. ; 
In Amblystoma, as in the frog, the olfactory bulb extends 
backward into the ventrolateral area, so that this area does not 
extend so far forward as does the dorsolateral (’10, figs. 10, 11). 
The arrangement of cells in the lateral wall of the hemisphere 
of Amblystoma is indicated schematically in figures 8 to 20 of 
my 1910 paper and in figures A to L of Bindewald’s description 
(14). 
The ventrolateral quadrant is much more simply organized 
than in the frog. The anuran corpus striatum and amygdala 
are here completely merged, though the fiber connections of this 
generalized region show that it contains the primordia of both 
of these structures. 
A thickening of the ventrolateral wall of the hemisphere at the 
level of the interventricular foramen, less sharply defined than 
in the frog, contains a considerable collection of nerve cells and 
a dense neuropil related chiefly to the lateral forebrain bundle 
and its commissure (figs. 24, 37). This clearly is the urodelan 
representative of the two separate areas in this region of the frog 
which have been already described. The diffuse ventrolateral 
olfactory tract cannot be traced definitely to any part of it, but 
its fibers are distributed apparently to the entire ventrolateral 
area, especially its rostral end. This thickening is the only 
well-differentiated structure in the lateral wall of the urodele 
cerebral hemisphere behind the olfactory bulb. Not to preju- 
dice its morphology at the start, it will here be termed the 
ventrolateral nucleus of the hemisphere. 
The rostral end of the ventrolateral area of the hemisphere 
appears to be physiologically dominated by the secondary olfac- 
tory fibers of the ventrolateral olfactory tract, that is, it is a por- 
tion of the lateral olfactory nucleus. The caudal end of this 
