456 THE INTERMEDIATE PRIMATES 



fourth and third cranial nerve nuclei. The griseal investment of the aqueduct 

 of Sylvius is relatively heavy. As the diencephalon is approached the ventro- 

 dorsal position of the central gray matter becomes more marked. Ventrally 

 it is continuous with the indifferent interpeduncular gray matter which 

 merges with that of the hypencephahc region. The lateral walls of the aque- 

 duct of Sylvius are continuous with the subependymal gray matter hning the 

 third ventricle. Dorsally the central gray matter fuses with the habenular 

 region. 



