TADPOLE LIPE. 11 



seen to progress," says Professor Owen, "witliout any inflection, 

 gliding slowly and with a ghost-like movement in a straight line, 

 and if the observer have the- nerve to lay his hand flat in the 

 reptile's course, he will feel, as the body glides over the palm, 

 the surface pressed as it were by the edges of a close- set series of 

 paper knives, successively falling flat after each application." 

 Others of the class, such as the Tortoises, Crocodiles, and Lizards, 

 move by the help of feet, which are generally small and feeble — 

 in a few species being limited to the pectoral region, while in 

 most both pairs are present. In some, as in various Lizards, the 

 limbs acquire considerable strength. 



There is one genus of small liizards, known as the Dragons, Draco, 

 whose movements present an exception to the general rule. Besides 

 their four feet, these animals are- furnished with a delicate mem- 

 branous parachute, formed by a prolongation of the skin on the 

 flanks and sustained by the long slender ribs, which permits of 

 their dropping from a considerable height upon their prey. 



Batrachians, again, difler from most other Reptilia by being 

 naked : moreover, most of them undergo certain metamorphoses ; 

 in the first stage of their existence they lead a purely aquatic 

 life, and breathe by means of gills, after the manner of fishes. 

 Young Frogs, Toads, and Salamanders, which are then called tad- 

 poles, have, in short, no resemblance whatever to their parents in 

 the first stage of their existence. They are little creatures with 

 slender, elongated bodies, destitute of feet and fins, but with large 

 heads, which may be seen swimming about in great numbers in 

 stagnant ponds, where they live and breathe after the manner 

 of fishes. By degrees, however, they are transformed: their 

 limbs and air-breathing lungs are gradually developed, then 

 they slowly disappear, and a day arrives when they find themselves 

 conveniently organized for another kind of existence ; they burst 

 from their humid retreat, and betake themselves to dry land. 

 " The tadpole meanwhile being subject to a series of changes in 

 every system of organs concerned in the daily needs of the coming 

 aerial and terrestrial existence, still passes more or less time in 

 water, and supplements the early attempt at respiration by pullu- 

 lating loops and looplets of capillaries from the branchial vessels." 

 (Owen.) 



