414 



THE INTERMEDIATE PRIMATES 



surface of this organ is sharply convex from side to side and thus forms a 

 decisive ridge in the midline of the cerebellum. This ridge becomes progres- 

 sively less distinct in the higher anthropoids and man. The divergence in 



FIG. ig3 DORSAL SURFACE OF BRAIN, HYLOBATES HOOLOCK. 



[Actual Length, 70 mm.] 



Key to Diagram, sulc. inter-par.. Sulcus Interparietalis, s. prec. inf., Sulcus Precentralis Inferior; sulc. 

 PRECNT. SUP., Sulcus Precentralis Superior; sulc. ret. inf., Sulcus Retrocentralis Inferior; s. ret. s., Sulcus 

 Retrocentralis Superior. 



the occipital portion of the superior longitudinal fissure of the higher forms 

 gradually lessens, with the general effect that the occipital region eventually 

 conceals from view the entire tentorial surface of the cerebellum. 



FISSURES AND LOBES 



In its fissures and lobations, also, the cerebral hemisphere corresponds 

 closely with the brain of the macaque and baboon. The fissure of Rolando 

 separates the frontal and parietal lobes, the Sylvian fissure intervenes between 

 the parietal and temporal lobes, the simian fissure separates the parietal 

 and temporal lobes from the occipital lobe. The convolutional pattern in all 



