nil- BRAIN OF MODERN MAN 823 



proniiiic'iice nia\ well decrease' in comparison \\\{h the more rix'cnt lunctional 

 accessions ol ihe ccrchelliiin represenlecl h\ the superior ceri'heMar pt'tluncle. 

 On the one hand, the uncniate tract cK'notes organization in the cerebellum 

 related to paleokinesis, particularix' concerned in the hahincino; mechanism, 

 while on the other hand, the superior cia't'ljehar pi'dunck' is an index of 

 developments in coordinativc control ol precise mo\ements expressing 

 neokinetic specialization. 



The outstanding feature at this level is the great increase in the size 

 of the pons \ arolil produced by the augmentation ol the pontile nuclei. So 

 marked is this expansion thai pontile structures ol the basis encroach upon 

 the tegmentum pontis to such an extent that some ol the pontile nuclei 

 actually lie dorsal to the mesial lillet ( PN, Mf). Such pontile encroachment 

 ma\' be looked upon as another e\'i(k'nce ol tlu' exuberant e\[3ansion of these 

 nuclear masses seeking accommodation in all a\ ailable regions. They appear 

 to extend caudally as a jirolongation ol the nuclear substance which forms 

 the nucleus arcilormis, and to some exti-nt mliltrate the mesial lillet. This 

 invasion ol the tegmentum is j)rimaril\ a human feature. Indications of it 

 may be lound here and there in the chimpanzee and in the gorilla, but in the 

 main no such massive extension of nuclear substance into the tegmentum is 

 witnessed m any other species as in man. 1 he basis pontis takes its character 

 much more Irom tliese nuclear aggregations than it docs even from the great 

 mass of transverse pontile libers which lurther increase the actual volume of 

 the pons N'arolii. 1 he arrangement ol the three layers m the pons is similar 

 to that noted in other species. All of tlu' pontile layers, the stratum super- 

 licialc pontis, the stratLim complexum pontis and the stratum prolundum 

 pontis luu'e their characteristic appearances. The manner in which the 

 transverse libers accumulate as they approach the lateral aspect of the 

 section to lorm tlu' middle ci'rebellar pi-duncU' 1 M ep ) is a feature which has 

 been noted in connection with each form of the primates discussed. In the 



