464 AMPHIBIA. 



while the paired adhesive sucker is less and less used, and 

 gradually disappears. The limbs bud forth, but the anterior 

 pair, hidden by the gill-covers, do not become visible so 

 soon as the posterior pair. When the tadpole is about two 

 months old, it has attained to the structural level of the 

 Dipnoan fishes ; it still has internal gills, but the lungs have 

 begun to be functional. The larvae come often to the surface 

 to breathe. 



We may now pass over tw^o or three weeks to the third 

 chapter in the history, when the tadpole begins to undergo 

 a remarkable metamorphosis. It rises above the structural 

 level of a fish, and becomes definitely an amphibian. It ceases 

 to feed on water-weeds. For a time it seems to fast, but it 

 is really living on its own tail, from which wandering leuco- 

 cytes absorb nutriment, and carry it to other parts of the 

 body. A casting of the outer layer of the epidermis takes 

 place. " The horny jaws are thrown off ; the large frilled 

 lips shrink up ; the mouth loses its rounded suctorial form 

 and becomes much wider ; the tongue, previously small, 

 increases considerably in size ; the eyes, which as yet have 

 been beneath the skin, become exposed; the fore-limbs 

 appear, the left one being pushed through the spout-Jike 

 opening of the branchial chamber, and the right one forcing 

 its way through the opercular fold, in which it leaves a 

 ragged hole." (Quoted from Milnes Marshall : The Frog; 

 an Introduction to Anatomy, Histology, and Embryology, 

 3rd ed. Manchester and London, 1888.) 



While these changes are in progress, and as the supply of 

 food afforded by the tail begins to be exhausted, the tadpole 

 recovers its appetite, but is now carnivorous, feeding on 

 available animal matter, and even on its fellows. At this 

 stage tadpoles will clean a skeleton beautifully, and Buckland 

 describes them as showing a great avidity for animal food, 

 crowding round a drowned kitten, and nibbling at the toes 

 of little boys who wade in the pools. 



With the change of diet, the abdomen shrinks, stomach 

 and liver enlarge, the intestine becomes relatively narrower 

 and shorter. The tail shortens more and more, and is at 

 last completely absorbed; the hind-limbs lengthen; the 

 animal leaps ashore— a small frog. 



It seems that for a considerable time the tadpole is neither 



