28 THE POPULAR SCIENCE MONTHLY. 



Next come the spider-monkeys, so called from their slender bodies 

 and enormously long limbs and tail. In these monkeys the tail is so 

 long, strong, and perfect, that it completely takes the place of a fifth 

 hand. By twisting the end of it round a branch the animal can swing 

 freely in the air with complete safety; and this gives them a wonderful 

 power of climbing and passing from tree to tree, because the distance 

 they can stretch is that of the tail, body, and arm added together, and 

 these are all unusually long. They can also swing themselves through 

 the air for great distances, and are thus able to pass rapidly from tree 

 to tree without ever descending to the ground, just like the gibbons 

 in the Malayan forests. Although capable of feats of wonderful agility, 

 the spider-monkeys are usually slow and deliberate in their motions, 

 and have a timid, melancholy expression, very different from that of 

 most monkeys. Their hands are very long, but have only four fingers,, 

 being adapted for hanging on to branches rather than for getting hold 

 of small objects. It is said that, when they have to cross a river the 

 trees on the opposite banks of which do not approach near enough for 

 a leap, several of them form a chain, one hanging by its tail from a 

 lofty overhanging branch and seizing hold of the tail of the one below 

 it, then gradually swinging themselves backward and forward till the 

 lower one is able to seize hold of a branch on the opposite side. He 

 then climbs up the tree, and, when sufficiently high, the first one lets 

 go, and the swing either carries him across to a bough on the opposite 

 side or he climbs up over his companions. 



Closely allied to the last are the woolly monkeys, which have an 

 equally well-developed prehensile tail, but better proportioned limbs, 

 and a thick, wholly fur of a uniform gray or brownish color. They 

 have well-formed fingers and thumbs, both on the hands and feet, and 

 are rather deliberate in their motions, and exceedingly tame and affec- 

 tionate in captivity. They are great eaters, and are usually very fat. 

 They are found only in the far interior of the Amazon Valley, and, 

 having a delicate constitution, seldom live long in Europe. These 

 monkeys are not so fond of swinging themselves about by their tails as 

 are the spider-monkeys, and offer more opportunities of observing how 

 completely this organ takes the place of a fifth hand. "When walking 

 about a house, or on the deck of a ship, the partially curled tail is car- 

 ried in an horizontal position on the ground, and the moment it touches 

 anything it twists round it and brings it forward, when, if eatable, it is 

 at once appropriated ; and when fastened up the animal will obtain any 

 food that may be out of reach of its hands with the greatest facility, 

 picking up small bits of biscuit, nuts, etc., much as an elephant does 

 with the tip of his trunk. 



We now come to a group of monkeys whose prehensile tail is of a 

 less perfect character, since it is covered with hair to the tip, and is of 

 no use to pick up objects. It can, however, curl round a branch, and 

 serves to steady the animal while sitting or feeding, but is never used 



