62 ANIMALS OF NO IMPORTANCE. 



is the first part to be set at liberty, the tadpole then adher- 

 ing to the egg by head and tail in the form of a loop. At 

 last perseverance is rewarded, and the young tadpole disen- 

 tangles itself; it rests awhile after having accomplished this 

 feat. The newly-hatched tadpole is about a third of an 

 inch long and quite black. Protruding from the neck are 

 two gills in the form of tufts. The tail is fringed by a soft 

 fin. On the head are two suckers, by means of which it 

 attaches itself to water plants or other objects. Tadpoles 

 possess horny jaws by means of which they crop the water 

 weeds upon which they feed and bite the urchins who fish 

 in the ponds on Clapham Common. Consequently tadpoles 

 are known as " toe-biters " to these fishermen. The tadpole 

 is undoubtedly a more or less faithful copy of an ancestor 

 of the frog. 



Long ages ago, when flying reptiles were the denizens of 

 the air, and deinosaurs and sea-serpents disported them- 

 selves in the ocean, there were no frogs. At that period 

 the development stopped at the tadpole state. As time 

 wore on, the conditions of amphibian life changed and with 

 them the tadpoles. Their external gills became covered by 

 a membrane and limbs appeared, so that they became able 

 to survive when the pools in which they lived became tem- 

 porarily dried up, just as the mud-fish are now able to. 

 These periods of terrestrial existence grew longer in suc- 

 ceeding generations ; meanwhile the legs increased in 

 magnitude, the tail disappeared, and lungs developed, so 

 that eventually the tadpole found itself changed into a frog. 

 The original transformation of the tadpole into the frog 

 occupied hundreds of thousands of years ; in the developing 

 frog the process is repeated in a few weeks. The lungs of 

 the frog are still very imperfect, being simple sacs, and there 

 are no respiratory movements of the chest. Breathing is 

 in great part effected through the skin. For this purpose 

 it is necessary that the integument should be damp ; conse- 

 quently whether frogs live on the ground or in trees, they 

 are never found far from water. As yet the frog is but im- 



