66 APES, MONKEYS, AND LEMURS 



as occurring in the gibbons, are invariably present. These callosities, which are 

 not unfrequently bright colored, afford another characteristic by which we can at 

 once distinguish an Old World monkey from any and all of its American cousins. 

 Their use is to afford a comfortable rest for the body in the upright sitting posture 

 assumed by the monkeys and baboons of the Old World. 



Another feature absolutely peculiar to the monkeys and baboons 



of the Old World, although by no means common to the whole of 



them, is the presence of those pouches in the cheeks, with which all 

 who have fed tame monkeys must be perfectly familiar. These cheek pouches are 

 formed by folds in the skin, and when empty lie flat on either side of the face. 

 They can, however, be so distended as to contain a large quantity of food, and then 

 stick out prominently on either side, so as to communicate a peculiarly bloated 

 appearance to the face. The possession of these pouches must obviously be a great 

 advantage to the monkeys in which they are found, since by their means a large 

 quantity of food can be hurriedly gathered, stowed away, and afterwards eaten at 

 leisure in some place of security. It might, indeed, be urged that the monkeys 

 which do not possess these convenient receptacles appear to get on in life quite as 

 well as their relations who are thus provided, and that, therefore, these pouches 

 are of no real advantage. To this it may be replied that such Old World monkeys 

 as have no cheek pouches feed much more on leaves and shoots than on fruits ; and 

 that they are furnished with a peculiarly complex stomach in which this food can 

 be rapidly stowed away previously to undergoing complete digestion. 



With regard to the limbs of the Old World monkeys and baboons, 



it may be observed that the arms never present that great excess in 

 length over the legs which we have seen to be the case among the Man-like Apes, 

 and the legs may, sometimes, be the longer of the two. The thumb of the Old 

 World monkeys and baboons can in all cases be fully opposed to the fingers, except, 

 of course, in the African species in which it is either absent or rudimentary, and 

 therein have another marked point of difference from the Amerian group. 



Finally, the skeletons of all members of the present group may be 



readily distinguished from those of the Man-like Apes by the breast- 

 bone being narrow and flattened from side to side, instead of broad and flattened 

 from back to front. Moreover, all of the species have a central bone in the wrist, 

 a characteristic they have in common with the gibbons and orangs among the 

 Man-like Apes. 



Such, then, are the leading features by which the monkeys and 



baboons of the Old World (forming a larger group than any other 

 in the order) are distinguished from the groups immediately above and below 

 them in the zoological scale ; and the reader who has followed us carefully thus far 

 ought to be able to tell at once whether any particular monkey that is set before 

 him should or should not be included in the present group. When we speak of the 

 members of this group occupying a position immediately below that of the Man- 

 like Apes, we must guard ourselves from conveying the idea that the one can in 

 any sense be regarded as the ancestor of the other. The difference in the structure 

 of the molar teeth of the two groups is alone sufficient to prove that this cannot be- 



