VIVIPAROUS AMPHIBIANS 35 



two pairs of gills on each side ; those of some tailed 

 forms (tritons, newts, etc.) have three pairs, while the 

 shape of the body, tail, limbs, and the niind)er of these 

 last and their toes are all different in different species. 

 The body in the tadpoles of frogs and toads is much 

 shorter than that of the tailed forms, and in the former 

 only there are sucking disks under the head. 



The c?ecilian tadpole shows a swimming tail, some 

 internal gills only, and in one kind the stump of a leg 

 — all of which are lost later when the creature begins 

 to burrow. 



YiviPARous Amphibians 



In many amphibians, as in fishes and reptiles, the 

 eggs are hatched in the body before they are laid. 

 In some instances the eggs are laid but are hatched 

 immediately. In a few cases the entire tadpole-state 

 is run within the body of the parent, and the young 

 are born in the complete form. A remarkable in- 

 stance is that of the Alpine salamander. Many eggs 

 are formed in the mother but two only are hatched. 

 All the others then run together in a mass to feed the 

 two growing tadpoles. These have very long bushy 

 gills whicli they lose at birth. They have been taken 

 from the mother before they were born and put into 

 w^ater, whereupon they lost their first gills at once, 

 but grew other new shorter ones — those by whicli they 

 breathed in the parent's body, being quite likely too 

 large for the much better aerated water. This, Mr. 

 Mivart, a great naturalist, has cited as an instance 

 where at once a creature could adapt itself to its sur- 



