INTRODUCTION 15 



departing from its more ancient patterns of hoof, paw or claw and assuming 

 the nearly complete grasping powers of the hand. The tail also, in certain 

 instances, participated in this specialization for arboreal locomotion. 



These physical modifications actuated by tree life were quite as emphat- 

 ically augmented by psychic influences arising from the new habitat. The 

 background of the lives of almost all of the primates has played a dominant 

 role in molding their behavior. The primeval forests and jungles, in their 

 perpetual semi-darkness, created a domain whose subtle powers made them- 

 selves felt in all primate reactions. It might be that the forest stood on the 

 edge of a wide plain with a clear opening from which to look across toward 

 the distant hills. The psychological effect of these factors, it must be clear, 

 determined certain decisive attitudes on the part of the animals toward their 

 environment. For example, there could not fail to be an alluring temptation 

 in the green plain and its expansive freedom. To venture into this open space, 

 however, the early primates required mechanisms \\hich they did not as 

 yet possess. Certain dangers lurked in and over the plain. Predatory creatures 

 of every kind were there — reptile, mammal and bird — lying in wait for just 

 such an excursion. For the time, at least, the semi-darkness was safer with 

 its limited view and real security in the upper highways out of reach of these 

 preying enemies. 



THE LEMURS AND TARSI ERS, SHOWING THE EARLIEST 

 MODIFICATIONS OF PRIMATE STRUCTURE 



With the lemurs, perhaps, there came the first modifications of structure 

 leading to the more conspicuous groups of the primate kind. These animals, 

 with their slender, furry bodies, their fox-like heads, their widely separated 

 eyes and bushy tails, showed in both hands and feet the beginning differen- 

 tiation of lingers and toes. This adaptation marks the transition from some 

 lower form of mammal to the primates. It was in an epochal modification 



