TARSIUS SPECTRUM 



95 



ever, the lack of fissures in the neopallium may be attrilmted to a retrograde 

 process in the cortex which, according to one interpretation at least, repre- 

 sents a secondary degenerate stage produced during the evolution of the 



FIG. 45. DORSAL SURFACE OF BRAIN OF TARSIUS SPECTRUM. 



[Actual Length, 21 mm.] 



Key to Diagkam. cerebel.. Cerebellum; front, lobe. Frontal Lobe; obl.. Oblongata; olf. bulb. 



Olfactory Bulb; sylv. fiss., Sylvian Fissure. 



Cebidae. The simple condition of the hemispheres of tarsius would seem, on 

 the other hand, to represent the retention of definitely primitive characters 

 in a brain in many other respects affected by marked progressive tendencies. 



ORBITAL CONCAVITIES AND OLFACTORY BULB 



The basal surface of the hemisphere presents two ill-defined orbital con- 

 cavities although the orbits in tarsius are extremely large. The lack of prom- 

 inence of these concavities is due to the fact that the frontal lobe is poorly 

 developed. The olfactory bulb is large, protruding rostrad in front of the 



