92 MARION HINES 
brain surface is foreshadowed in the structure of embryo no. | 
940. 
The morphological changes found in this embryo as compared 
with the 14-mm. embryo are as follows: 
1. Acceleration of the neopallium and appearance of temporal 
pole. 
2. Appearance of the fissura hippocampi. 
3. The invagination of the lamina epithelialis, forming the 
lateral choroid plexus. 
4. Increase in length of the lamina terminalis, and the appear- 
ance of the angulus terminalis. 
5. The acceleration of the medial component of the caudate 
complex. 
6. Great growth of the midthalamic region. 
The 20-mm. embryo, Mall Collection, 460 (fig. 17) 
The development of the central nervous system as a whole is 
practically identical with that attained by H 173, the 19.1-mm. 
embryo (compare figs. 15 and 16 with 17). In this case also only 
the telencephalon and part of the diencephalon was modeled. 
Consequently, the morphological description must be confined 
especially to the growth of the forebrain vesicle. 
The relation of structures in the telencephalon medium are 
the same as those found in H 173. The angulus terminalis is 
essentially the same. And as noted before, the lamina terminalis 
is divided into two regions. The diencephalic limb of the velum 
transversum forms a small elevation which marks the posterior 
boundary of the foramen interventriculare (fig. 17, For. int.). 
The anterior extremity of the sulcus limitans coincides with the 
suleus which divides the corpus striatal complex from the hypo- 
thalamus. This rostral end of the limitans was called sulcus 
Monroi by His. Milhalkovics, quoting Richert, however, in- 
cludes in the suleus Monroi not only the rostral end of the sulcus 
limitans, but also the sulcus separating the medial limb of the 
striatal complex from the diencephalon. 
