32 REPTILE GALLERY. 



which are gradually exchanged for lungs ; in some Batrachians 

 in which the larva is to some extent a vegetable-feeder, the change 

 from mixed to an exclusively animal diet is accompanied by a 

 shortening of the intestine ; and in many the loss of a tail is com- 

 pensated by the growth of four limbs, whilst in others the tail is 

 persistent throughout life. The metamorphosis is very complete 

 in Frogs and Toads, in which the limbless, long-tailed larva or ' Tad- 

 pole' differs so much from the perfect animal that only direct 

 observation can afford the proof of these changes being the develop- 

 mental stages of the same creature. However, a few Tailed Batra- 

 chians (Proteidm, Sirenidos) retain the gills throughout their 

 existence, though producing one or two pairs of limbs ; and a certain 

 number ofFrogs belonging to various genera [Rana, Hylodes, Rhino- 

 derma, Pipa, &c.) are known to leave the egg in the perfect form. 



The greater number of Batrachians are oviparous ; some, like 

 the Salamander, are ovoviviparous. The eggs are deposited in 

 water or damp places, and generally (in all the British species) 

 enveloped in a gelatinous capsule, which protects them from mecha- 

 nical injury and atmospheric influences : those of the Frogs form 

 large coherent lumps, whilst the Toads deposit theirs in long 

 strings, and the Newts attach theirs singly to water-plants. In 

 a few species the female carries the eggs in a pouch on her back 

 INototrema), or in dorsal cells (Pipa), or attached to her belly 

 (some Rhacophori) ; in a few the male carries the eggs round his 

 legs [Alytes) or in a gular sac [Rhinodermd).- 



The tongue is occasionally absent ; when present it is generally 

 attached to the front end of the floor of the mouth instead of, as 

 in the higher Vertebrates, at the hinder end; in the majority 

 of the Tailless Batrachians it can be thrust out of the mouth, 

 and act as the organ with which they seize their prey. (See 

 fig. 25, p. 37.) 



In many species a sac or a pair of sacs are developed on the 

 throat or the side of the head in the males ; they act as resonants 

 to the waves of sound set up by the air which is passing from the 

 lungs, and the species that possess them are much more noisy than 

 those that are without them. 



All Batrachians have numerous small glands imbedded in their 

 skin for the secretion of a whitish slimy fluid. In some these gland.s 



