CHAPTER X. 
HOMOLOGIES AMONG CRUSTACEA. 
LIVING crayfish can be bought in the markets of 
large cities. One or two of these should be kept in an 
aquarium with several inches of water in a place where 
the class may study their structure and their move- 
Fig. 87.—Side View of Crayfish, an, antenna; r, rostrum; cep, cephalic 
portion; tho, thoracic portion of cephalothorax; ab, abdomen. 
ments before attempting the laboratory exercise on the 
shrimp. 
Feed the crayfish with pieces of meat or fish, and 
note the manner of seizing and eating food. 
Touch the antennae with various substances. See 
“Outline for Requirements in Zoology ” printed by 
Harvard University. 
Notice how the crayfish walks and how it swims 
backward when disturbed. 
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