406 NILS HOLMGREN 
the hippocampal. In the section before us this connection is 
nearly broken off. This condition probably is the consequence 
of the development of the inner general pallial cortex (g.p.c.). 
In the preceding stages this cortex was quite ventricular in posi- 
tion. Now it is separated from the ventricle by a cell-poor space 
and has assumed the characters of a thick special cortical layer. 
The preparations give the impression that the growth of this 
cortex should be the reason for the breaking of the primordial 
connection between the hippocampal and the pyriform cortex. 
Below the general pallium the ventricular neuroblastic layer 
seems to be in activity, forming new nerve cells, but the activity 
is not very rapid (the ventricular cell-layer having not increased 
much during the period from 5- to 6.5-em. body length) except 
at one point, viz., medially below the hippocampal rudiment. 
Here there is a very pronounced emigration of cells (h.em.) 
towards this rudiment. The hippocampal rudiment in this sec- 
tion appears as a nearly vertical, short lamella (h.c.) of densely 
packed cells. Ventrally this cell formation is limited by the 
obsolete zona limitans medialis, dorsally it insensibly merges into 
the above-mentioned lamina of scattered cells, connecting it with 
the pyriform lobe. Laterally the hippocampal rudiment is con- 
tinuous with the emigrating cells (h.em.) mentioned above. 
C. Cross-section through the tip of the recessus neuroporicus 
(fig. 13). The olfactory bulb rudiment is touched at its cephalic 
side. The most striking feature of this section is that the pyri- 
form lobe (p.c.) is quite dorsal in position. The portion occupy- 
ing in the preceding section the lateral part of the brain vesicle 
has disappeared and the corresponding part in this section is 
filled up by seattered cells. A closer analysis of this field of 
scattered cells shows that it represents the zona limitans, which 
has bent upward in such way that it is here cut longitudinally 
(z.L.l.).. The upper border of this field lies lateral to the pyri- 
form lobe, and in the consecutive sections the zona here bends 
caudally again on the lateral border of this lobe, above the 
olfactory bulb rudiment. 
The general pallial cortex (g.p.c.) covers the main part of the 
dorsal aspect of the section. Outside of it there are some scat- 
