BATRACHIA 



127 



in cloudy, wet weather. They return to ponds and brooks in 

 spring at the time for laying eggs. This time for both frogs and 

 toads is shown by trilling. All frogs, except tree frogs, remain in 

 or near the water all the year. 



Fig. 248. — Metamorphoses of the Frog, numbered in order. 



Do eggs hatch and tadpoles grow more rapidly in a 

 jar of water kept in a warm place or in a cold place t 

 In pond water or in drinking water? Can the tadpoles be 

 seen to move in the eggs before hatching ? When do 

 the external gills show ? (Fig. 248.) 



What parts may be described in a tadpole ? What is 

 the shape of the tail? Compare the tadpole with the fish 

 as to (1) general 

 shape, (2) cover- 

 ing, (3) fins, (4) 

 tail, (5) gills. 



Do the exter- 

 nal gills disap- 

 pear before or after any rudiments of limbs appear ? 

 (6, 7, Fig. 248.) Can you locate the gills after they be- 

 come internal ? (Fig. 249.) 



FlG. 249. — Tadpole, from below, showing intestine 

 and internal gills. (Enlarged.) 



