398 BATRACHIA. 



Second Subclass. BATRACHIANS. 



Only one ventricle of the heart ; atruim incompletely divided into two. 

 Passing- a metamorphosis. Breathing* by gills in an early stage of their 

 development, the gills being permanent in some species. Two occipital 

 condyles. 



This Subclass comprises the Order of Tailless Batrachians (Bateachia ecaudata s. sali- 

 entia), p. 398, that of Tailed Batrachians (Bateachia caudata s. gkadientia), p. 438, and 

 that of Burrowing Batrachians (Bateachia apoda), p. 440. 



THE ORDER OF TAILLESS BATUACHIAN^—B JTRJCHL4 



SALIENTIA. 



Body broad, short, in the perfectly developed state with four legs and 

 without tail. 



The Batrachians are distinguished from the other divisions of the vertebrate animals by 

 their passing through a metamorphosis — that is, after their embryonal life, undergoing changes 

 which affect not only their external form, but also their internal organs. The Tailless 

 Batrachians, or the Frogs and Toads, have in their perfect condition a short, broad body, 

 ■without a caudal appendage, and with four limbs, the posterior pair being much stronger 

 and longer than the anterior, and specially suited for leaping or swimming or burrowing. 

 Many species have an interdigital web, and the degree of its development between the hind 

 toes in different species indicates theii- respective power of swimming. Such a membrane 

 between the fore toes is found only in some of the climbing forms, which always have the 

 extremities of the toes dilated into round disks. The food of the Batrachians consists of 

 insects and worms, and only the largest kinds feed on small vertebrates also ; they seize their 

 prey with the clammy tongue, either filliping it out of the mouth, as those do which have 

 their tongue adherent in front and free behind, or only turning it out when that organ is 

 nearly entirely attached to the bottom of the mouth. Teeth are never found in the lower 

 jaw, which is a simple, feeble arch, and only a few species have a pair of tooth-like pro- 

 minences near the symphysis; on the other hand, the upper jaw and the vomer are very 

 frequently armed with a series of feeble teeth, which in the largest species assist in seizing 

 the food. The prey is swallowed entire. 



Moisture is as necessaiy for Batrachians as food and air, hence they are found only in damp 

 places or in the neighbourhood of water ; and when the hot season commences, Batrachians 

 li\ing remote from water bury themselves deep enough in the ground to escape the exsic- 



