2630 FROGS AND TOADS 



The frogs and toads are distinguished from their allies by the pres- 

 Charactenstics ence o f f our ii mDS an( j the absence of a tail in the adult state; the 

 d T^d ^ atter f eature giving origin to the name Ecaudata, by which the order 

 to which they belong is scientifically designated. They all have short 

 and frequently thick bodies, in which the backbone comprises, at most, only eight 

 vertebrae in advance of the sacrum; those behind the latter being fused into a long 

 rod-like bone, as shown in the figure of the skeleton on p. 2626. In the fore-limb, 

 as shown in the same figure, the bones of the fore-arm (radius and ulna) are com- 

 pletely fused together; and the same is the case with regard to the tibia and fibula 

 in the hind-leg. Moreover, the hind-limb obtains a kind of additional segment, 

 owing to the elongation of the calcaneum and astragalus in the ankle joint, which 

 form a pair of long bones lying parallel to one another. As a rule, frogs and toads 

 undergo a lengthened larval period; the " tadpoles," as shown in the figure on p. 

 2627, having a globular head and body, a fish-like tail, external or internal gills, 

 and no limbs in the first stages of their existence. The hind-limbs are the first to 

 appear, and after the front pair are developed the tail is gradually absorbed upon 

 which the young for the first time leave the water. Represented by about a thou- 

 sand species, frogs and toads have a world- wide distribution, although more abun- 

 dant in tropical and subtiopical than in temperate regions, and being especially 

 numerous in India and South America; and it is not a little remarkable that some 

 of the largest forms are inhabitants of islands. From the nocturnal habits of the 

 adults it is frequently difficult to find out whether in any locality these reptiles are 

 abundant or the reverse; but in the spring this may generally be ascertained by ob- 

 serving the tadpoles in the rivers and points. 



THE TYPICAL FROGS 

 Family RANIDsE 



The typical frogs, together with four other families, constitute a suborder 

 (Firmisternia) characterized by the presence of a tongue, and by the firm union of 

 the two metacoracoid bones of the chest by means of a single cartilage uniting their 

 free edges. From the other members of the group, the typical frogs are distin- 

 guished as a family by the presence of teeth in the upper jaw, and by the transverse 

 processes of the sacral vertebra being either cylindrical, or but very slightly dilated 

 at their extremities. These characteristics are sufficient to distinguish the typical 

 frogs from the other families of the suborder; but it may be added that the vertebras 

 are cupped in front and hollowed behind; while there are no ribs; and the terminal 

 style of the backbone is articulated to the sacrum by two condyles. The terminal 

 joints of the toes may be either simple or pointed, T-shaped, Y-shaped, or even 

 claw-like; the species in which these joints are thus expanded having the soft parts 

 similarly expanded and flattened. For a long time it was considered that the shape 

 of the tips of the toes was connected with the mode of life of their owners; and al- 

 though this is so to a great extent, it is now ascertained that several of the species 



