THE AMYGDALA IN AMPHIBIA 229 
Mingled with the fibers of the amygdalo-habenular tract are 
others passing between the septum and the habenula (fig. 18, 
tr. s. hab.), the tractus septo-habenularis of my earlier account 
(10, pp. 426, 428). Some of these fibers apparently decussate 
in the anterior commissure in company with those of the tractus 
amygdalo-habenularis. ° 
The tractus amygdalo-habenularis of this description was 
designated in the former paper (710, pp. 429, 444) tractus habenulo- 
striaticus. Our preparations do not indicate the direction of 
conduction of its fibers. This tract contains the only myelinated 
fibers related with the amygdala of the frog. The tractus strio- 
thalamicus which I mentioned (’10, p. 444) as related with this 
region is connected with the true corpus striatum (whose limits 
at that time were not clearly defined) and has nothing to do with 
the amygdala. 
Note ON THE TRACTUS OLFACTO-HABENULARIS ANTERIOR. In all 
species of Amphibia which I have studied there is a connection (which 
was overlooked in my paper published in 1910) between the ventral part 
of the septal region near its rostral end and the habenula, which I shall 
term the tractus olfacto-habenularis anterior. This clearly defined 
tract of unmyelinated fibers passes caudad along the extreme ventral 
surface of the cerebral hemisphere, and at the rostral end of the lamina 
terminalis occupies the angle between this structure and the ventral 
border of the prominentia fascicularis (figs. 14 to 18). It then turns 
abruptly dorsad and caudad to join the tractus cortico-habenularis 
lateralis in the angle between the dorsal border of the prominentia 
fascicularis and the posterior pole of the hemisphere. In the latter 
part of its course it is a thin sheet of fibers forming the most super- 
ficial layer of the prominentia fascicularis. The less densely stained 
fibers of the diagonal band form an intermediate layer between these 
and the longitudinally directed fibers of the lateral forebrain bundle. 
Tractus amygdalo-piriformis. There is a broad connection 
between the amygdala and the overlying pyriform lobe, probably 
of mixed character. For the observed relations see the account 
of the dorsal olfactory projection tract below. 
The diagonal band of Broca. From the entire lateral surface 
of the amygdala very fine unmyelinated fibers assemble in diffuse 
formation and turn ventralward in a narrow zone external to 
the lateral forebrain bundle and, farther forward, ventrally of it. 
