i6 INTRODUCTION 



such as this that the primate order had its origin. Then began a tenancy 

 of the trees which profoundly influenced these animals as they passed 

 through their many and varied adaptations. Tarsius, in many respects 

 even more than the lemurs, illustrates the eflects ot these new mlluences. 



THE CEBIDAE FORESHADOWERS OF A NEW RACE 



It is dillicult to discern the exact point at which the Hapalidae, most 

 familiarly represented by the diminutive marmosets, took departure irom 

 the early beginnings of this primate line. Their appearance on the scene was 

 probably a retrogressive step in the development of the new-world monkeys. 

 Their small size, their lack oi power both m body and brain, would scarcely 

 permit of a dominating ad|ustment to then- envnonment. In many respects 

 their organization was inferior to that of the lemurs. This is particularly true 

 in their manual ditTercntiation, since the development of their fore- and hind- 

 limbs tended much more toward claws than hands. Nevertheless, for all 

 their insignificance, there was that about them which suggested the 

 coming of a new race. The configuration of the head, the expression of 

 the face, the relation of the eyes, the shape of the nose, the position of the 

 mouth, all were prophetic of the more definitely ape-like tribes which 

 were to follow. The arrival of the new-world monkeys at length intro- 

 duced all of the major simian characters. Throughout the large family 

 of the Cebidae, quadrumanal development is well established. Most of the 

 members of this group have also acquired prehensile tails. 



INFLUENCES ACTIVATING MODIFICATION WHICH PRODUCED OLD-WORLD 

 CONGENERS OF PRIMITIVE SIMIANS 



What influences activated the modification which produced the old- 

 world congeners of these South American simians is not clearly understood. 

 It may have been a progressive tendency to increase in weight, added to the 



