218 RALPH EDWARD SHELDON 
posterior tuberis. (Tractus habenulo-diencephalicus, figs. 77, 
79, 80, 82, 83, 100, 101.) Excepting its most rostral part, it is 
closely associated with the medial forebrain bundle dorsally, 
which probably accounts for the rarity with which it has been 
reported. Apparently most of its fibers decussate in the habenu- 
lar commissure, but such could not be demonstrated with cer- 
tainty. ; 
The tractus habenulae ad prosencephalon of Goldstein, the trac- 
tus ad proencephalon of Edinger, was not identified. Of course, 
it is quite possible that some of the fibers of the tractus olfacto- 
habenularis are ascending, as Goldstein believes. 
No optic connections with the habenulae could be found, as 
Bela Haller describes. Large numbers of cells lying in the nu- 
cleus posthabenularis, particularly near the median ventricle, 
give rise, however, to fibers which pass directly laterad to enter, 
apparently, the optic apparatus as Haller notes (figs. 76, 77, 79, 
83). These require further study. Considering the intimate 
relation between the nucleus posthabenularis and the ganglia 
habenularum, an optic connection, such as Haller describes, not 
improbably exists in some forms. 
(4) Posthabenular-preoptic connections. In addition to the 
connections already described with the fasciculus retroflexus and 
the. optic apparatus, the nucleus posthabenularis is placed in 
relation with the nucleus preopticus through three sets of diffuse 
unmedullated fibers, a tractus preoptico-posthabenularis, pars 
anterior from the nucleus magnocellularis to the nucleus post- 
habenularis; a tractus preoptico-posthabenularis, pars posterior 
from the nucleus parvocellularis posterior, and the tractus post- 
habenulo-preopticus from the nucleus posthabenularis to the 
nucleus parvocellularis posterior (fig. 140). 
It is evident from its position and connections that the nucleus 
posthabenularis is closely related with the habenulae. ‘The two 
are evidently a morphological entity, the habenular ganglia devel- 
oping as specialized portions of the dorsal lamina of the thalamus. 
(5) Epiphyseal fibers. Along the caudal wall of the epiphysis 
runs a small medullated bundle, which extends caudad to the 
posterior commissure. It is possible that it gives off fibers to the 
