150 STUDIES, SCIENTIFIC AND SOCIAL chap. 



American monkeys, which are really more different from 

 all those of the Old World than any of the latter are from 

 each other. Naturalists, therefore, usually divide the 

 whole monkey-tribe into two great families, inhabiting 

 the Old and the New Worlds respectively ; and, if we 

 learn to remember the kind of differences by which these 

 several groups are distinguished, we shall be able to 

 understand something of the classification of animals, and 

 the distinction between important and unimportant 

 characters. 



Taking first the Old World groups, they may be thus 

 roughly defined : — apes have no tails ; monkeys have tails, 

 which are usually long ; while baboons have short tails, 

 and their faces, instead of being round and with a man- 

 like expression as in apes and monkeys, are long and 

 more dog-like. These differences are, however, by no 

 means constant, and it is often difficult to tell whether 

 an animal should be classed as an ape, a monkey, or a 

 baboon. The Gibraltar aj)e, for example, though it has 

 no tail, is really a monkey, because it has callosities, or 

 hard pads of bare skin on which it sits, and cheek pouches 

 in which it can stow away food ; the latter character being 

 always absent in the true apes, while both are present in 

 most monkeys and baboons. All these animals, however, 

 from the largest ape to the smallest monkey, have the 

 same number of teeth as we have, and they are arranged 

 in a similar manner, although the tusks, or canine teeth, 

 of the males are often large, like those of a dog. 



The American monkeys, on the other hand, with the 

 exception of the Marmosets, have four additional grinding 

 teeth (one in each jaw on either side), and none of them 

 have either callosities or cheek pouches. They never 

 have prominent snouts like the baboons ; their nostrils 

 are placed wide apart and open sideways on the face ; 

 the tail, though sometimes short, is never quite absent ; 

 and the thumb bends the same way as the fingers, is 

 generally very short and weak, and is often quite wanting. 

 We thus see that these American monkeys differ in a 

 great number of characters from those of the Eastern 

 hemisphere ; and they have this further peculiarity, that 



