386 



THE INTERMEDIATE PRIMATES 



portion of the rndbrain which in the primates has gained particular promi- 

 nence. In all probability, httle of the primordial responsibility for the function 

 ot vision is still vested in the superior colhcuii. This portion of the brain, 



FIG. lOI. MACACUS. LE\EL OF THE SUPERIOR COI LICULUS. 

 CEN, Central Gray Matter; cp. Cerebral Peduncle; ctt, Centra! Tcgemental Tract; mf. Mesial Fillet; 

 MGB, Mesial Geniculate Body; noc, Oculomotor Nucleus; XRU, Nucleus Ruber; N3, Oculomotor Nerve; pd, 

 Predorsal Bundle; pl, Posterior Longitudinal Fasciculus; rep, Reticular Formation; sc, Superior Colliculus; 

 SBN, Substantia Nigra; spt, Spinothalamic Tract. (Accession No. 149. Section 381S. Actual Size 19 X 10 mm.] 



which tor such a long period in vertebrate e\'ohition held dominance in the 

 animal's visual functions, has now become much reduced in this respect and 

 appears as a relatively insignificant structural tcature on the dorsal surface 

 of the midbrain. As a matter of fact, the superior colliculus is somewhat 

 larger than the inferior colliculus, and it still retains some degree of stratihca- 



