458 THE INTERMEDIATE PRIMATES 



or baboon. As already noted, the hind legs are short and afiord but imperfect 

 means of locomotion upon the ground. Its fore extremities, on the other hand, 

 are most highly specialized for arboreal locomotion, the forearm being long, 

 out of all proportion to the requirements essential for other skilled perform- 

 ances. The hand likewise has developed few of the more generalized 

 capacities seen in other forms, but is particularly specialized as a swinging 

 hook for reaching and grasping the branches as the animal makes its 

 flight-like passage. In this light the behavioral development of gibbon 

 accords well with the relatively low planimetric coefficient of its pyramidal 

 development. 



Both the macacus and the baboon are about ecjual in the planimetric 

 coefficients of the pyramidal system, a fact which points to a behavioral 

 development nearly on a par in these two species. Although macacus is essen- 

 tially a tree-dwelling form, and the baboon mainly ground-living in habit, 

 in both the development of hand and foot is essentially equal. Whatever 

 slight advantage exists in the pyramidal comparison of the baboon and maca- 

 cus favors the latter, a relation which is in harmony with the behavioral dif- 

 ferences in these two forms. The macaque is recognized to be more adaptable 

 and is measurably more teachable than the baboon. The motor specialization 

 of the former would thus be expected to be somewhat greater than that of the 

 latter. 



The planimetric coeflicicnts of the pyramidal system of the intermediate 

 primates are given in the appended tabulation: 



Planimetric Coefficients of the Pyramidal System 



