16 INTRODUCTION. 



sions, are nevertheless able to slowly ascend a pane of 

 glass. 



In most of our genera the fourth and fifth toes are 

 cleft almost to the base, and the metatarsal portions of 

 them are separated by the web. In two genera, Bufo 

 and Eyla, this is not the case; the metatarsals of the 

 two outer toes are bound together by the common 

 integument, the angular divergence of the fifth toe 

 proceeding only from the basal phalanx, as may be 

 seen from the following figures (Fig. 6) representing 

 the foot of the common frog and that of the tree- 

 frog. 



Fig. 6. 



Lower surface of foot of Rana temporaria (a) and Hyla arborea (b). 



The tree-frog differs from other Batrachians in 

 having the articulations of the limbs, especially the 

 wrist, marked above by a strong fold, reminding one 

 of the arms and legs of a jointed 'papier-mache doll. 



The proportions of the hind limbs to the body are 

 best appreciated by bending the limb forwards against 

 the si^e, and ascertaining the position of the tibio- 

 tarsal or tarso-metatarsal articulation ; a certain allow- 

 ance must, however, be made in cases w^hen the abdo- 

 men of a female is much distended with ripe ova. A 

 convenient method of appreciating the length of the 

 tibia as compared to the femur is to fold the limb so 

 as to place the former at a right angle to the axis of 

 the body, as shown in the accompanying figure (Fig. 7) ; 

 in which position the heels (tibio-tarsal articulation) 

 meet when the tibia is nearly equal to the thigh, fail 

 to meet when shorter, or overlap when longer. 



