INTRODUCTION 191 



pair of orifices, the choance^ or inner openings of the 



nostrils ; there is also in most Anura a pair of inner 



ear-openings {Eustachian tubes). The tongue, which is 



absent in a few of the tailless batrachians, may be more or 



less completely adherent to the floor of the mouth, or 



fixed only in front, or so constructed as to be protensible 



to a very considerable distance, as in Chameleons. 



The tail of the Urodeles is cylindrical in the land forms, 



more or less compressed in those living in the water ; in 



the European newts of the group known as Euproctus, the 



organ is prehensile. In the Anura the tail is absent ; 



in the Apoda it is also absent or extremely short. The 



fore and hind limbs in the Urodeles are usually of 



nearly equal length, while in the Anura the latter 



are usually much the longer, and adapted for leaping ; 



they are provided with four fingers and five toes in most 



forms, although the digits may, as in some Urodeles, be 



reduced to two only. The fingers are usually free, while 



the toes are often provided with an extensive web. In 



some Frogs both hand and foot are webbed to such an 



extent that, as in the arboreal Bornean species of Rhaco- 



phorus, they have been reported to serve as a parachute to 



the creature when it leaps from branch to branch. Arboreal 



species have the tips of the digits more or less strongly 



dilated, and by means of these discs they are able to attach 



themselves to smooth surfaces, as in the Geckos. The discs 



do not act as suckers, as is generally believed, but adhere 



by the intense pressure of certain muscles, supplemented 



by a sticky secretion. The adhesion is not usually effected 



entirely by the feet, but to some extent by the suctorial 



action of the belly, which is developed to a certain extent 



