674 C. JUDSON HERRICK AND JEANNETTE B. OBENCHAIN 



Fig. 9 Section through the thiilamus three sections (45 m) farther caudad than 

 figure 8 and passing through the common vertical ridge formed by the medial and 

 ventral lobes of the thalamus. 



Fig. 10 Section through the rostral end of the tuberculum posterius. The 

 letters s.l. mark the position of the sulcus limitans, which appears clearly defined 

 a few sections farther caudad. The elements of the cell plate below this level 

 are somewhat larger and more loosely arranged than those above it. 



Fig. 11 Section through the posterior commissure and the caudal end of the 

 recessus mammillaris. 



Fig. 12 Section through the midbrain immediately in front of the commissura 

 posterior tecti, illustrating the characteristic internal structure at the site of the 

 sulcus limitans, through the sulcus itself is not evident on the ventricular sur- 

 face (cf. fig. 3). 



