32 FISH GALLERY. 



which are gradually exchanged for lungs • in some Batrachians 

 in which the larva is a vegetable-feeder, the change from a vege- 

 table to an animal diet is accompanied by a shortening of the 

 intestine; and in many the loss of a tail is compensated by the 

 growth of four limbs, whilst in others the tail is persistent through- 

 out life. The metamorphosis is very complete in Frogs and Toads, 

 in which the limbless, long-tailed larva or f Tadpole ' differs so 

 much from the perfect animal that only direct observation can 

 afford the proof of these changes being the developmental stages of 

 the same creature. However, a few Tailed Batrachians (Proteida, 

 Sirenida) retain the gills throughout their existence, though pro- 

 ducing one or two pairs of limbs ; and a certain number of Frogs 

 belonging to various genera (Rana, Hylodes, Rhinoderma, 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 mass, 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 

 (Nototrema) , 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 (Rhinoderma). 



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 glands 



