124 SEA-SHORE LIFE 
at times of low tide. This siphon may be as much as a foot in 
length, and is pierced by two tubular openings, the one nearest the 
hinge side of the clam serving to carry off the digested food, and 
water from the gill chambers, while the other serves to admit water 
into the gill chambers of the clam. There is thus a constant cur- 
rent going into and passing out of the siphon. The shell is quite 
thin and brittle. This clam spawns in early summer, and the eggs 

Fig. 82; SOFT-SHELL CLAM. From life. Annisquam, Mass. 
develop into little free-swimming larve which soon settle down 
upon seaweed or other submerged objects and attach themselves 
by means of a thread called a byssus, which is secreted by a gland 
in the foot of the little clam. Soon they free themselves and sink 
to the bottom, where they begin to burrow when about one-quarter 
of an inch long. They still attach themselves to particles of 
sand, however, and often leave one burrow to construct another. 
Finally, however, they dig a permanent burrow which they rarely 
or never leave, and no longer produce a byssus. 
This valuable mollusk is highly esteemed in the market. The 
fishery in the New England States is worth more than $500,000 
annually. 
