1897.] NATURAL SCIENCES OF PHILADELPHIA. 55 



A reasonably good conception of the mechanism of the foot is 

 secured by placing it longitudinally on the upper surface of a small 

 rounded stem. The pollex holds to the side of the stem, the short 

 second and third digits to the top, and the longer fourth and fifth 

 digits to the outer side. These dispositions show how well adapted the 

 foot is for both support and prehension. The method of progression 

 accepted by the animal is not so well shown. But doubtless the 

 "spring" of the limb enables the foot to quickly let go its hold. 

 The arrangement might be called one for longitudinal perching as 

 contrasted to the transverse perching of birds and the chameleon. 

 If the view here expressed be accepted, the positions in which the 

 foot is drawn by Burmeister and Brehm are erroneous. In Bur- 

 meister's memoir the grasp is that of the human hand, the thumb be- 

 ing on one side of a small bough and all the other digits on the other. 

 In the main figure of Brehm u the foot is transverse to the bough. 

 In the smaller figure it is longitudinal. But the bough is so large 

 in the illustration that it makes but little difference what the posi- 

 tion of the foot may be. Cuvier 15 represents the foot in the position 

 here claimed on anatomical grounds to be correct for small boughs. 

 The inference to be drawn is the following : Tarsius is specially 

 adapted to spring lightly along small boughs and limbs of trees by 

 the longitudinal perch. It may modify the grasp on large, broad 

 su rfaces. 



"Thierleben, I, 274. 

 15 Regne Animal. 



