NATURAL HISTORY STUDIES 



to feed eagerly, nibbling at plants in the water, 

 and also eating animal food. As a consequence it 

 grows, and the food-canal, in particular, becomes 

 very long and coiled like a watch-spring. As the 

 tail becomes stronger and the power of locomotion 

 increases, the horseshoe -shaped adhesive organ is 

 converted into two small discs which gradually 

 disappear. 



Different Stages of Tadpoles 



A new stage is marked by the appearance of the 

 hind-limbs as minute projecting buds at the boun- 

 dary between trunk and tail. The fore-limbs are 

 delayed by the gill-cover, which does not impede 

 the hind-limbs, but they eventually emerge, the 

 left one through the breathing-hole, the right one 

 by a breakage. 



After the appearance of the hind-legs, the larvae 

 come often to the surface to breathe. They are 

 learning to use their lungs, which have been slowly 

 developing for some time as pockets projecting 

 into the body-cavity from the under side of the 

 gullet. The tadpoles are now about two months 

 old, and in having lungs as well as gills they may 

 be compared to the double-breathing mud-fishes 

 or Dipnoi. As the lungs begin to be used, the gills 

 dwindle away, and the fish-like heart and circula- 

 tion become those of a frog. 



From Tadpole to Frog 



After a period of hearty feeding, with consequent 

 increase in size and strength, the tadpole begins 



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