388 THE INTERMEDIATE PRIMATES 



tance has already been mentioned in connection with the development of 

 binocular vision. Special reference is made to them in this phice in order that 

 their significance in the animal's behavior may be subsequently discussed. 



FIG. 183. MACACUS. LE\EL OF THE ANTERIOR COMMISSURE. 



AC, Anterior Commissure; cin. Internal Capsule; fdp, Descending Pillar of the Fornix; for, Fornix; len. 

 Lenticular Nucleus; NAT, Nucleus Anterior Thalanii. [Accession No. 149. Section 565. Actual Size 30X8 mm.] 



Ventral to the nucleus oculomotorius, although as yet poorly differentiated, 

 is the ULicIeus ruber (NRu) through which some of the emergent fibers 

 of the oculomotor nerve pass. Lateral to this nucleus is the reticular forma- 

 tion ( Ref ), whose general appearance suggests the lack of highly special- 

 ized differentiation in this species. The lateral portion of this formation is in 

 continuation with a small protuberance on the lateral surface ot the midbrain, 

 the mesial geniculate body ( Mgb) which serves as one of the relay stations 

 in the secondary pathway of hearing. 



The \'entral aspect of the section shows a cleft in and about the mid- 

 line. This is the beginning of the optico-peduncular space which sepa- 

 rates the basis into the right and left cerebral peduncles (CP). These 



