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Pearl divers.
CHAPTER IX
MOLLUSKS
The Fresh-water Mussel
Suggestions.—The mussel is usually easy to procure from
streams and lakes by raking or dredging. In cities the hard-shelled
clam, or quahog, is for sale at the markets, and the following
descriptions apply to the anodon, unio, or quahog, with
slight changes in regard to the siphons. Mussels can be kept
alive for a long time in a tub with sand in the bottom. Pairs of
shells should be at hand for study.
External Features.—The shell is an elongated oval,
broader and blunter at one end (Fig. 188). Why does
the animal close its shell? Does it open the shell?
Why? Does it thrust the foot forward and pull up to it,
or thrust the foot back and push? (Mussels and clams
have no bones.) Does it go with the blunt or the more
tapering end of the shell forward? (Fig. 188.) Can a
mussel swim? Why, or why not?
