THE BRITISH AMPHIBIANS. 133 



gills and a horse-shoe shaped sucker on the under side of the head 

 with which it clings to water-plants and other objects. Then the 

 depression in the front of the head deepens and opens into the alimen- 

 tary canal, thus becoming the mouth with which the tadpole feeds 

 on vegetable matter. As the locomotive powers improve, the sucker 

 splits into two and is gradually disused. The external gills are 

 soon replaced by an internal set enclosed in chambers, by the 

 growth of the folds of which they are eventually closed in, with the 

 exception of an aperture on the left side through which the water 

 taken in by the mouth is ejected after passing over them. The hind 

 lirnbs then begin to show, the front pair being hidden in the gill- 

 chambers. The lungs, developed from the gullet, get to work at the 

 same time as the hind legs, and the tadpole, about nine weeks old. rises 

 to the surface to breathe air direct and feeds greedily on the water 

 weeds. This is followed by a period when it seems to have no relish 

 for its food, the tail shortens, the horny jaws are lost, the 

 frills on the lips shrink, the mouth widens, the tongue grows larger, 

 the eyes come through the skin, and the fore legs appear, one 

 through the gill aperture, the other through a hole it pushes for 

 itself in the right opercular fold. Meanwhile the tadpole has begun 

 to feed again, but has changed its diet; from being mainly a 

 vegetarian it has become exclusively a carnivore, eager, when 

 opportunity serves, to feed on younger tadpoles- And as it feeds 

 the intestines become more and more adapted for dealing with 

 animal food, the abdomen shrinks, the tail shrinks, the legs lengthen, 

 and as a frog it leaves the water for the land, to return to it only in 

 the breeding season and in times of danger. 



The Common Frog is about three inches in length. It is almost any 

 shade of brown above, with blackish spots, the males being yellowish 

 white below and the females orange, the males being further recog- 

 nisable by the black swollen cushion on the inner side of the first 

 finger. The vocal sacs are internal, and when in use bulge out the 

 skin of the throat below the angle of the mouth. It ranges over the 

 whole of Europe and right across Africa. 



The Edible Frog is rather larger. It is greenish above, with a 

 pale stripe down the middle of the back, the blackish markings being 

 very distinct. The under parts are smooth, but on the upper parts 

 are a few warts and glandular folds. The male is distinguishable 

 by the grey pad on the inner side of the first finger, and by the 

 external vocal sac behind the angle of the mouth, which is distended 

 when used until it is almost as large as a cherry. It is more aquatic 

 in its habits than the common species, and ranges further south and 

 east, crossing the Mediterranean into Northern Africa, and appear- 

 ing in Japan. In England it is confined to the eastern counties, 

 while the common frog is found everywhere, even in Ireland. The 

 common frog is the brown frog or grass-frog ; the edible frog is the 

 green frog or water-frog. Both feed on insects, worms, and snails, 

 and other animals in a small way, not excepting younger frogs in all 

 stages, these being flicked down the throat by the curious tongue, 

 which is worked from the front of the mouth instead of from the back. 

 The green frog has a much louder and more musical note than the 

 brown frog, and his vocal efforts take the form of a regular series of 

 solos and choruses. 



