LEMUR MONGOZ 



37 



necessary to the coordinative regulation of skilled movements. The small 

 size of the pons in lemur thus suggests a poor capacity on the part of the 

 animal to acquire or execute even a comparatively snnple series of skilled acts. 



FIG. U). RIGHT LATERAL SURFACE OF BRAIN, LEMUR MONGOZ. 



[Actual Length, 45 mm]. 



Kev to Diagram, c, Sulcus Centralis; obl.. Oblongata; sulc. orb.. Sulcus Orbitalis; sulc. temp, sup.. 



Sulcus Temporalis Superior. 



The Dorsal Surface of the Brain Stem. The dorsal surface of the 

 brain stem in its axial portion is concealed by the overlapping cerebellum 

 which presents a vermis with t\\o small but well-marked lateral lobes. 

 These lobes are clearly separated from the vermis by two distinct lateral 

 paramedian sulci. 



The small cerebellum of lemur emphasizes its limited range of skilled 

 performances, especially as regards skilled acts of the upper extremities in 

 purposes other than those essential to locomotion (Fig. i6). 



When the cerebellum is removed by section through its peduncles, the 

 dorsal aspect of the brain stem in its axial portion is revealed. The oblongata 

 presents its typical ventricular and infraventricular portions. In the infra- 

 ventricular area the dorsomedian seam indicates the line of fusion between 

 the two alar plates of the bulb. The eminences of the clava and cuneus are 

 not prominent. In the ventricular portion of the oblongata the gradual 

 divarication ot the alar plates exposing the floor of the fourth ventricle follows 

 the same general outline as in other mammals. The inferior triangle of the 



