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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