ioi8 



ENOLLTIONAL MODIFICATIONS 



discretely occipital or not, this contingent of the pa>ii/-|^..;\to-cerebeIIar 

 system •■'-'-f- ■r>+..^ry exists. It arises, p>erhaps, in some common ground in 

 which tii^ ^MastivicTS of the parietal, of the tempKjral and of the occipital 



COMPAR.\TI\ E PLAMMETRIC GRAPHS 



B. Pontile Nuclei 



FIG. j\0. GKAPU BASED ON PLAMMETRIC INDICES OI- THE PONTILE NUCLEI. 



From this graphic comparison it is apparent that the pons Varolii, like other structures in the brain stem 

 associated with neokinetic evolution, expands rapidly in passing upward through the several horizons of 

 the primate order. Prior to this level of vertebrate organization pontile development is relatively insignifi- 

 cant and the structure is absent in all orders below the class of mammals. The pons Varolii is essential to the 

 finer coordination of the more highly organized .skilled acts. 



