410 NILS HOLMGREN 
the forebrain is attained in principle. The inversion of the pallial 
parts has become much greater than in the preceding stage. The 
general pallial thickening has been bent down to a vertical posi- 
tion in the upper part of the ‘septum’ partly between the hippo- 
campal cortex and the ventricular wall. In the subpallial parts 
a corresponding process has taken place, and the medial part of 
the tuberculum olfactorium cortex is also brought to a vertical 
position. The forward evagination of the forebrain vesicle - 
also is much more pronounced, the ‘septum’ thus having increased 
considerably in length. At the foramen monroi, where the 
‘septum’ is broken off, the pallial part of it is separated from the 
subpallial. 
1. Pallial parts. The hippocampal cortex is very clearly seen 
in the front part of the ‘septum,’ where it is confluent with the 
pyriform cortex (fig. 18). The upper end of the hippocampal 
cortex is bordered by more densely arranged and dark-staining 
cells (fig. 19, swb.). This border or cell-lamina lies inside of the 
medial part of the general pallium (fig. 19, g.p.c.), which is bent 
down to a vertical situation (fig. 10) in the upper part of the 
‘septum.’ The mentioned border has the appearance of a 
‘subiculum’ as found in reptiles. It begins as soon as the separa- 
tion of the hippocampal and pyriform cortex has taken place and 
in front of the general pallium. 
The hippocampal cortices are joined with each other by a 
cellular bridge dorsal to the recessus neuroporicus (figs. 20, 21). 
This seems to be a result of the secondary medial fusion of the 
evaginated parts of the forebrain, which had already taken place 
dorsal and ventral to the tube-like recessus neuroporicus. 
The general pallial cortex has grown much thicker than before, 
the medial swelling being now voluminous and sharply bent 
down medially in the ‘septum’ (fig. 1, g.p.t.). Towards the fora- 
men monroi, where the general pallial cortices are confluent 
dorsally (fig. 22, g.p.c.), the medial parts are very voluminous, 
causing at the foramen monroi a thick ridge hanging down from 
the roof of the ventricle (fig. 22). The main part of the ‘epis- 
phaerium’ of Edinger is made up by the general pallium (figs. 22, 
