THE THUMB IN MONKEYS 



appears, according to the traveller Bates, to be easily 

 accomplished by Cebus albifrons. Their agility can be 

 readily studied at the Zoo, though the limited range for 

 leaping and climbing renders it a little difficult to 

 compare, and award the palm satisfactorily. 



The general characters of the Platyrrhine form of 

 monkey can be as well studied in these monkeys as in 

 any other. The widely separated forwardly and not 

 downwardly directed nostrils, the prehensile tail, are 

 all obvious ; but it will be hardly possible to note in 

 the living monkey the thirty-six teeth, which are four 

 in excess of the teeth of the monkeys of the Old World, 

 including man. 



SPIDER MONKEY 



There are several kinds of spider monkey, perhaps 

 ten. But they all agree in representing the Platyrrhine 

 characters, or at least one of them, in a quite exaggerated 

 fashion. The prehensile tail is eminently prehensile, 

 its tip naked beneath to afford a securer clutch ; it is 

 never at rest even when not in use as a " fifth hand " ; 

 perpetually does it explore the objects lying above the 

 monkey's back, like the restless tentacle of an anemone. 

 The name spider monkey refers to the straddling and 

 spider-like appearance presented when one of these 

 monkeys is grasping various objects with hands, feet, 

 and tail widely divaricated and radiating from the 

 small body in the centre. The spider monkeys of the 

 New World suggest the gibbons of the Old. In many 

 monkeys the thumb has become somewhat rudimentary ; 

 in A teles, as the spider money genus is termed, it has 

 often disappeared. But the reason for this, or at least 

 a reasonableness in the fact, is evidenced when it is 

 considered that the hand of these and many monkeys is 

 of the nature of a hook to grasp temporarily a branch 



40 



