CHAPTER XVI. 
THE STRUCTURE AND ACTIVITIES OF A FISH. 
Goldfish or other small fish from streams or 
ponds are easily kept in aquaria. With a few living 
fish placed where pupils can observe them, and a 
smelt or perch from the market as an individual 
specimen for study on each bench, the following ques¬ 
tions may be answered: 
Shape and Covering. Is the fish bilateral ? Esti¬ 
mate length, thickness, and depth. 
What is the shape of the body ? 
Do you find a head ? a neck ? 
Do you find scales ? Do they cover the entire 
animal ? 
Are the scales joined edge to edge ( tesselated ) or 
do they overlap {imbricated)? 
Remove some of the skin. What is the appearance 
of the muscle below ? 
Notice the line extending along the side of the fish 
from head to tail {lateral line). Do the scales cover¬ 
ing this line differ from those found elsewhere on the 
body ? 
The Fins. How many fins do you find ? How 
many are dorsal ? How many ventral ? How many 
are paired ? 
Which fins correspond to the limbs on our own 
bodies ? 
The paired fins nearest the head of the perch are 
called the pectoral fins, those somewhat farther back 
nearer the anal opening are called the pelvic fins. The 
large fin along the back is the dorsal fin. The unpaired 
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