CHAPTER XVII. 
TADPOLES AND FROGS. 
In the study of the frog, aquaria are indispensable. 
The expense, however, need not be large. In one 
aquarium tadpoles should be placed together with a few 
aquatic plants. The minute green plants which grow 
on the sides of the aquarium will furnish food enough. 
The adult frogs can be kept in a box with glass sides 
with only a small amount of water in the bottom and 
a netting to cover the top. In warm weather frogs 
feed on insects; in winter they go without food. 
The Tadpole. Is it bilateral ? 
Is the skin naked or scaly ? Do you see a lateral 
line ? 
In what ways does it resemble a fish ? 
How does the tail of a tadpole differ from the tail of 
a fish ? 
In any of the tadpoles can you see the beginnings of 
limbs ? Which limbs appear first ? 
In a young tadpole how do the gills appear ? 
Can you see the gills in an older tadpole ? Do tad¬ 
poles come to the surface of the water to breathe ? 
Can you find in a specimen which has been hardened 
in alcohol a gill-cavity ? Can you find an opening into 
this cavity ? 
Are the jaws hard or soft ? Watch the tadpoles 
feeding on the sides of the aquarium, or jar. 
How does the size of the mouth compare with that in 
the adult ? 
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