HANDS AND FEET. 287 



structure and function ; though none have so well-developed a 

 thumb, and none can point with the index-finger. In certain 

 Apes of Asia {Semnopitheci) the thumb is very small, and in 

 closely allied African forms (Colobi) it is wanting altogether, 

 being merely represented by a bony rudiment beneath the skin. 

 The very same defect is found in certain American Monkeys 

 (Atelcs); but others have a thumb fairly long; in none, however, 

 is it opposable as in man and the monkeys of the Old World, but 

 is rather like a fifth finger, bending round nearly in the same 

 plane as the other fingers, as may any day be seen by anyone 

 who will give a nut to one of them in our Monkey-house. 

 In all Apes the nails are much as in man, except in the 

 Marmozets, where they take the form of long pointed and curved 

 claws. As to their feet, the Apes of both worlds agree in having 

 a great toe (or hallux) set out at an angle with the other toes, 

 and thoroughly opposable. It no longer, as in man, serves as a 

 fulcrum in walking, but is a most powerful grasping organ, being 

 strongly drawn against the other toes by the action of the 

 "peroneus longus" muscle. The hallux is never wanting, as is 

 the pollex, but it may be very small, as in the Marmozets and 

 Orang. It may be nailless, as in the Orang, or support the 

 only flat nail, as in the Marmozets. In Apes, which climb so 

 much, the hands are largely locomotive, and they may act as the 

 lower ends of a pair of crutches, as in the anthropoid Apes which 

 rest their knuckles on the ground in walking. Nevertheless the 

 feet are the main locomotive and the hands the main prehensile 

 organs, and thus physiologically as well as anatomically Apes 

 may be said to have " two hands and a pair of feet." 



The Lemurs and their allies (representatives of which groups 

 may be found in the Monkey-house) have a certain superficial 

 resemblance to Apes, but show one or two odd peculiarities in 

 their extremities. Both pollex and hallux are well developed; 

 but the index of the hand tends to be small, and may even, as in 

 the Potto, be represented only by a minute rudiment. It is a 

 three-fingered lemuroid. The Aye-Aye (Chiromys) has the 

 middle finger much lengthened and extremely attenuated, the 

 utility of which condition is problematical. The foot, in the 

 Lemur, has always a sharp claw on the second digit, but in 

 certain genera {Galago and Chirogaleus, and especially Tarsius) 

 the foot is formed in a way found in no other beast whatsoever. 



