44 STUDIES IN LIFE AND SENSE. 



remarked, are not " quadrumanous " in any sense. A curious fact, 

 however, remains to be noted. Although the thumb is "unoppos- 

 able" to the other fingers, the muscles which, in the typical " hand," 

 give to the thumb its well-known powers of movement, are repre- 

 sented in the fore-limb of the marmosets. Such a fact would seem 

 to indicate either extensive modification of a once-useful hand, or 

 the beginnings and possibilities, under suitable conditions, of hand- 

 like functions being assumed by these animals. In respect of their 

 teeth, whilst the marmosets possess the same number of teeth as man 

 and the Old World apes namely, thirty-two these organs are dif- 

 ferently arranged from those of their higher neighbours. The 

 marmosets possess four front teeth, two eye teeth, six premolars, and 

 four molars or grinders in each jaw ; whereas in man and higher 

 apes four premolars and six molars are found in the jaw-armature 

 above and below. Squirrel-like in appearance, the marmosets 

 resemble these familiar quadrupeds in their habits. They are 

 fruit-eaters, but do not disdain an insect-diet, and they appear to 

 live in families in the trees. Whilst monkeys produce, as a rule, but 

 one young at a birth, the marmosets may produce as many as three. 

 A singular fact of their anatomy is found in the large size of their 

 true brain (or cerebrum\ the halves of which overlap the lesser brain 

 (or cerebellum] so as to cover the latter, when the brain is viewed 

 from above. Such a conformation is usually associated with a high 

 type of brain, but its occurrence in the marmosets does not appear to 

 be accompanied by any special development of intelligence. 



The remaining representatives of the Platyrhine, or New World 

 monkeys, agree in possessing for the most part " prehensile " tails ; 

 that is, a tail, the extremity of which can be utilised to grasp such 

 objects as the boughs of trees. The tail may lose this power, as in 

 the Sakis and squirrel monkeys (Callithrix, &c.); and it may be 

 short, as in the Brachyuri\ but no New World monkey absolutely 

 wants the tail a condition typically seen in certain of the Old World 

 apes. In such monkeys as the Ateles^ one of the spider monkeys, 

 and the howlers (Mycttes), the tail attains its highest development as 

 a prehensile organ. It is less powerful in the little Sapajous or 

 Capuchins. So powerful is the tail in the Ateles, that its designation 

 of a " fifth hand " is seen at once to be well merited. By its aid, 

 this monkey can suspend itself from the bough of a tree, with hands 

 and feet free to grasp any object and useful for the performance of 

 any function. It is naked beneath at the tip in the Ateles, and 

 thus serves the more efficiently as an organ of seizure j whilst in the 

 Capuchins the tail is hairy at the extremity. The adaptation to a 

 life amongst trees, is well seen in such a conformation as that found 

 in the tail of these Platyrhine monkeys. That such adaptation has 

 been of general and universal character is proved by the fact that 



