Amphibians 



237 



Adult amphibians are carnivorous. They all eat 

 lesser animals in great variety. Frogs and toads have 

 a projectile and adhesive tongue which is of great service 

 in capturing flying insects; but they eat, also, many 

 other less active morsels of flesh that they find on the 

 ground or in the water. 

 The food of some of the 

 lesser stream-inhabiting 

 salamanders , such as 

 Spelerpes, is mainly in- 

 sects, while that of the 

 vermilion-spotted newt 

 is mainly molluscs. 



The amphibia are a 

 group of very great bio- 

 logical interest. They 

 represent a relatively 

 simple type of vertebrate 

 structure. Their devel- 

 opment can be followed 

 with ease and it is illumi- 

 nating and suggestive of 

 the early evolutionary history of the higher verte- 

 brates. They illustrate in their own free-living forms 

 the transition from aquatic to terrestrial life. And they 

 show in the different amphibian types many grades of 

 metamorphosis. The transformation is more extensive 



FIG. 143. Diagram of individual eggs 

 from the egg mass of the toad and 

 seven species of frog occurring at 

 Ithaca. Eggs solid black; gelati- 

 nous envelopes white. (After 

 Wright). 



A, Toad, eggs in double gelatinous tubes, form- 

 ing strings, the inner tube divided by cross 

 partitions; B, pickerel frog; C, peeper (no 

 outer envelope) ; D, green frog (inner en- 

 velope ellipitical) ; E, tree frog (outer en- 

 velope ragged); F, bull frog (no inner 

 envelope); G, leopard frog; H, wood frog. 

 All twice natural size. 



FIG. 144. The spotted salamander, Ambystoma tigrinum. 



