90 MARION HINES 
fixed point from which to measure the growth of contiguous 
structures? . One thing is certain, it breaks the midline into 
two divisions, a ventral and a dorsal, whose ultimate outcome in 
development is characteristic. The ventral limb is thicker than 
the dorsal limb. It is the lamina terminalis. 
In figure 14 (14 mm.) the dorsal part, or pars tenuis ia 
of the lamina terminalis is much longer than the ventral or 
massive part (p.c.); but in figure 16 (19.1 mm.) these two parts 
are approximately the same in length. The former subdivision 
has been called by Johnston (13) the lamina supraneuroporica. 
It is a convenient name. The writer would like to use it, but 
there seems to be no evidence for as complete a separation be- 
tween the two portions of the terminal plate as Johnston thinks; 
‘and, since the last point of closure of the neural tube may lie 
anywhere, for aught we know, between the recessus preopticus 
and the velum transversum, it cannot be used to divide 
the Jamina into two morphologically distinct regions. At 
present the writer thinks there is no fundamental difference in 
the later stages between the ventral and the dorsal portions of 
this area, either in development or internal structure. 
The dorsal limb of the angulus terminalis (fig. 16, Ang. term.) is 
divided into two regions, the anterior that of the tela chorioidea 
telencephali medii (fig. 16, Tel. ch. tel. med.) and the posterior, 
that of the paraphyseal arch (fig. 16, Par. ar.). Extending 
laterally into the two ventricles from this arch are the two 
lateral choroid plexuses. These plexuses are connected across 
the midline by the vault (here the paraphyseal arch) of the 
foramen interventriculare (fig. 16), but are not connected pos- 
terior to the velum transversum. Here they form a broad 
shallow fissure in the medial wall, known as the fissura chorioidea. 
Bailey (16a) has called this the posterior limb of the plexus 
and that adjoining the paraphyseal arch, the anterior limb. 
Moreover, dorsal to this fissure in the medial wall of the 
hemisphere and extending more rostrally is a shallow groove. 
This groove can be followed as an indentation in the medial wall 
from a region slightly anterior to the angulus terminalis, caudal- 
ward to the tip of the temporal pole. This insignificant furrow 
