THE AMYGDALA IN. AMPHIBIA 247 
others and they have not been separately followed in our prepara- 
tions. ‘The dorsal olfactory projection tract, comparable with 
the tractus pallii of fishes, is, however, clearly defined. The 
observed relations are indicated diagrammatically in figure 37. 
The entire course of the dorsal projection tract is visible in the 
Golgi preparations from which figures 26 to 31 were drawn. 
These are horizontal sections through the brain of larval Ambly- 
stoma, and numerous other preparations by various methods 
show that the relations of the tract are essentially similar in 
the adult. These figures are drawn from consecutive. sections 
arranged in order from dorsal to ventral. 
Beginning the description at the caudoventral end of the tract 
and following it forward, we notice that the hypothalamic nucleus 
of the tract lies relatively farther ventral and caudal than in 
Anura. It is an ill-defined group of neurons (none of which are 
impregnated in this preparation) lying in the central gray of the 
hypothalamus at the caudoventral border of the chiasma ridge. 
Some of its neurons are seen in figure 32. The nucleus is filled 
with a very dense neuropil derived from several sources and 
takes the form of a crescent which crosses the midplane in the 
chiasma ridge, the horns being directed caudad into the hypo- 
thalamus (figs. 31 to 34). Within this neuropil are free end- 
ings of the fibers of the projection tract, many of which 
decussate just before terminating. 
From the nucleus the tract passes dorsally and slightly laterally 
across the posterior border of the chiasma ridge, here being 
surrounded by fibers of the medial forebrain bundle (fig. 30). 
Upon reaching the level of the lateral forebrain bundle the tract 
turns abruptly forward embedded within the other fibers of the 
ventral border of this bundle (figs. 28 to 30), and at the lateral 
border of the ventrolateral nucleus of the hemisphere its fibers 
scatter throughout the neuropil of this nucleus (figs. 26, 27). — 
In none of the urodeles which I have examined, either larval 
or adult, is the olfactory projection tract related to a special part 
of the ventrolateral nucleus of the hemisphere, but its fibers are 
mingled with those of the lateral forebrain bundle in a common 
neuropil. On the other hand, the tract itself is as large and 
