198 RALPH EDWARD SHELDON 
tion of the cells here included under the name nucleus preopticus. 
Bela Haller noted the same group of cells and termed it the 
nucleus posterior of the forebrain. Johnston (’98) and (01) found 
a nucleus bordering the recessus preopticus and termed it the 
nucleus thaeniae owing to the fact that he observed fibers passing 
from it to the habenula, and that, therefore, it is (98) ‘‘a nucleus 
corresponding to the nucleus occipito-basalis of (C. L.) Herrick 
and the nucleus thaeniae of Edinger” in reptiles. This view is 
untenable as will be pointed out later. Johnston probably recog- 
nized the fact, as he terms it nucleus praeopticus in his ‘Nervous 
System’ (06). Kappers noted the large cells and, following Her- 
rick, named the group, nucleus praeopticus. Goldstein, follow- 
ing the descriptions of Edinger for the brains of reptiles and birds, 
applied the names magnocellularis and parvocellularis strati grisei 
to the two components of the nucleus. 
(g) Nucleus entopeduncularis. Appearing immediately cau- 
dal to the nucleus commissuralis lateralis is a group of very small 
cells (fig. 65), lying embedded in the basal forebrain bundle (figs. 
66, 67, 68, 70). This is the nucleus entopeduncularis of Gold- 
stein. 
3. THE DIENCEPHALON 
a. Rostral limits 
The division of the vertebrate brain into transverse segments, 
with a clear definition of their limits, is a matter of considerable 
difficulty, particularly since, as Johnston and C. J. Herrick have 
pointed out, most of the important morphological centers and 
fiber connections are arranged in longitudinal columns. The 
question of the caudal boundary of the telencephalon ventrally 
is still unsettled, some authors considering the pedunculi thalami, 
caudal to the anterior commissure, part of the diencephalon, 
others placing the rostral limits of the ’tween-brain behind the 
optic chiasma in the adult. Dorsally the caudal margin of the 
velum transversum has long been considered the limit of the fore- 
brain. Johnston recently (’09) has taken up the subject in some 
detail and his interpretation is here followed; according to which 
