MORPHOLOGY OF THE FOREBRAIN 459 



western United States. In this animal the nucleus lateralis 

 septi is smaller than in many other lizards. 



In the lamina terminalis (fig. 61) the precommissural body has 

 risen above the preoptic recess and forms the "bed" of the com- 

 missures. It is broken up by the fiber tracts of the anterior 

 commissure, commissura pallii anterior and fornix into detached 

 clusters of cells, one which (n.c.p.), extends caudad above the 

 interventricular foramen as in larval Lacerta. The section figured 

 is slightly oblique, the left side being farther caudad and showing 

 the relations immediately rostral to the foramen. The relations 

 of this nucleus to the commissura pallii posterior caudad of the 

 foramen are seen in fig. 62. Dorsally of these parts of the pre- 

 commissural body is a small residue of the primordium hippo- 

 campi, filled with fibers of the fimbria. The fissura arcuata is 

 incomplete, not being marked on the ventricular surface, this 

 region being invaded by the nucleus lateralis septi. The cortex 

 of the dorso-medial wall (cortex hippocampi) is much more highly 

 developed, with more numerous and more densely crowded cells, 

 than is any other part of the cortex. Fig. 62 is taken through the 

 foramen interventriculare on the right side and the commissura 

 pallii posterior just behind the foramen on the left. On each side 

 is seen a small remnant of both the precommissural body (n.c.p.) 

 and the primordium hippocampi. 



Figs. 63, 64 and 65 illustrate horizontal sections through the 

 brain of another lizard, Sceloporus. The sections are slightly 

 oblique, the left side being a little farther dorsal than the right. 

 The left side of fig. 63 shows the dorso-median cortex at its great- 

 est extent, a condition which prevails at all levels dorsally of the 

 one figured. Immediately ventrally of this level, as shown by the 

 right side of fig. 63, the caudal wall of the hemisphere becomes 

 membranous and the thick primordium hippocampi appears in 

 the median wall. Fig. 64 passes through the interventricular 

 foramen on the right side and shows more densely crowded masses 

 of cells surrounding the foramen ; these belong to the precommis- 

 sural body. The left side shows that this nucleus extends above 

 the foramen also as nucleus of the commissura pallii posterior 

 (n.c.p.). Rostrally of the foramen is the thick septum, which is 



