EN'OLLTIONAL MODIFICATIONS 



primates of this ave been described from fossil remains by Professors 



Matthews and Grecor\-. 



Thenex" - ^ with the advent of light lemuroid 



prirr.ates. v. - was stUI of the slow, cautious, climbing type, 



__, dutch-like grip. All of the digits of the manus 

 _er, but the outer two were esp>ecially elongated. Similar modifi- 

 er ffccted the foot, so that the entire adaptive change established a 

 ?trnr_ >i:manal tendency. Pedal fulcrumation was still of the tarsal 

 n hallux and p>ollex were well developed. Modern examples 

 of this s: _ X found in loris and potto. 



A more decisive advance made its appearance when arboreal locomotion 

 combined the advantages of climbing with leaping. Passage through the 

 trees row became swifter and more effective. A tendency to semi-erectness 

 S' eloped, and the squatting posture was well established. The digits, 



metacarpals, tarsus and metatarsals all elongated, giving the quadrumanal 

 differentiation still greater prominence. Fulcrumation advanced to the 

 meta: > ~, thus p>ermrtting of a greater leverage in the take-off for leaping. 

 The hallux and p>olIex were more powerful and definitely opposable. The 

 forms most representative of this stage are lepidolemur and notharctus; 

 with these should be included the leaping tarsioids, and especially the 

 Indrisinae. 



From leaping and climbing it was but a short step to the stage of swing- 

 ing, cursorial locomotion through the trees. At this time brachiation was first 

 introduced, and had its far-reaching influence ujxtn all subsequent developn 

 ment. Swinging by the hands from branch to branch naturally lengthened 

 and strengthened the arms. The manus developed a suspension grip which 

 caused the digits to elongate, although the thumb underwent reduction, or 

 even, as in the spider monkey, did not appear at all. The foot developed a 

 grasping grip, and all of its elements elongated. Pedal fulcrumation was 



