MONKEYS -AFFINITIES AND DISTRIBUTION 151 



many of them have prehensile or grasping tails, which are 

 never found in the monkeys of any other country. This 

 curious organ serves the purpose of a fifth hand, and it 

 has so much muscular power that the animal can hang by 

 it easily with the tip curled round a branch ; while it can 

 also be used to pick up small objects with almost as much 

 ease and exactness as an elephant's trunk. In those 

 species which have it most perfectly formed it is very 

 long and powerful, and the end has the under side covered 

 with bare skin, much resembling that of the finger or 

 palm of the hand and apparently equally sensitive. One 

 of the common kinds of monkeys that accompany street 

 organ-players has a prehensile tail, but not of the most 

 perfect kind ; since in this species the tail is entirely clad 

 with hair to the tip, and seems to be used chiefly to 

 steady the animal when sitting on a branch by being 

 twisted round another branch near it. The statement 

 is often erroneously made that all American monkeys 

 have prehensile tails ; but the ftict is that rather less than 

 half the known kinds have them so, the remainder having 

 this organ either short and bushy or long and slender, 

 but entirely without any power of grasping. All prehen- 

 sile-tailed monkeys are American, but all American 

 monkeys are not prehensile-tailed. 



By remembering these characters it is easy, Avith a little 

 observation, to tell whether any strange monkey comes 

 from America or from the Old World. If it has bare seat- 

 pads, or if when eating it fills its mouth till its cheeks 

 swell out like little bags, we may be sure it comes from 

 some part of Africa or Asia ; while if it can curl up the end 

 of its tail so as to take hold of anything, it is certainly 

 American. As all the tailed monkeys of the Old World 

 have seat-pads (or ischial callosities as they are called in 

 scientific language), and as all the American monkeys 

 have tails, but no seat-pads, this is the most constant 

 external character by which to distinguish them ; and 

 having done so we can look for the other peculiarities of 

 the American monkeys, especially the distance apart of 

 the nostrils and their lateral position. 



