149 
46 
Figs. 42 to45 Pen drawings of sections through the 39.1-mm. embryo, H 163. 
The planes of section are indicated on the drawing of the model, figure 18. 
Fig.42 Through the septum and the postoptic recess. 
Fig. 43 Through the rostral portion of the lamina terminalis. The cortical 
lamination in the hippocampus reaches almost to the sulcus limitans hippo- 
campi. The differentiation of the pyramidal cell layer seems tardier than that 
of the polymorphous layer. 
Fig. 44 This section was taken through a more caudal part of the lamina 
terminalis. The slight groove in the medial wall, dorsal to a line joining both 
sulci limitantes hippocampi is the remnant of the fissura, hippocampi of the earlier 
stages. The polymorphous and pyramidal cell layers are not well as differen- 
tiated in the regio hippocampi as they are in the two previous figures. 
