106 MARION HINES 
In figure 25 also on the right side reading from the midline 
lateralward, the following histologically distinct areas are found: 
1) the telencephalic roof plate, i.e., the paraphyseal arch (Tel. 
r. pl.); 2) region of the future lamina epithelialis (not labeled) ; 
3) an area which will contain the fornix and the fascia dentata 
(compare the older embryo, fig. 14); 4) separated from the lamina 
epithelialis by a ventricular sulcus (Sul. vent.), the sulcus limitans 
hippocampi, is the primordium of the future hippocampus (Prim. 
hip). The sulcus limitans hippocampi can be traced from the 
caudal level of the paraphyseal arch (fig. 11, Reg. par. ar.) to a re- 
gion immediately anterior to the most rostral extent of the arch. 
This ventricular marking delimits areas at this stage of develop- 
ment already histologically distinct. This sulcus, together with 
the clear marginal velum lateral to it, enables the writer to bound 
accurately the anlage of the hippocampus. These slight early 
differentiations are of great importance, because they can be 
used as landmarks from which to measure the further growth and 
differentiation in the telencephalon. 
The 14-mm. embryo, Mall Collection, 940 (figs. 26 to 28) 
The counterpart of the distinct histological structures, dorsally 
placed in the telencephalon of the 11.8-mm. embryo, are found 
either in the unevaginated midline little changed or in the medial 
wall of the hemisphere of the 14-mm. The hemispheres of this 
brain extend for an appreciable distance anterior to the lamina 
terminalis and posterior to the velum transversum. In order to 
facilitate the description of the shifting position of histologically 
distinct areas, especially anterior to the lamina terminalis, within 
the developing hemisphere, they may be divided into quadrants 
(following the morphological terminology of Herrick, 710). In 
that paper Herrick suggested a subdivision of the amphibian 
cerebral hemisphere into four fundamental quadrants, viz., dorso- 
lateral (pyriform lobe); 2) dorso-medial (primordium hippo- 
campi); 3) ventro-lateral (striatum complex); 4) ventro-medial, 
septal complex. To these in mammals there is added (p. 496) 
a fifth region, the neopallium. In this embryo (14 mm.) these 
regions can be recognized save for the confusion of the pyriform, 
