THE CLAM AND OTHER BIVALVED SHELL-FISH. 69 



We will for a moment look at the life of an oyster. It 

 may be divided into three periods. 1. The fry. In about six 

 hours after life begins the germ swims about in the water, 

 and in a few hours more looks as represented in Fig. 69, i. 



FIG. 69. 1. Young oyster seen from the side immediately after fixation by the 

 mantle border (HI); r, ciliated velum, or paddle; si, four young European oys- 

 ters taken from the beard of the parent, enlarged !)t> times ; 6, very young spat, 

 showing the peculiar form of the true larval shell and that of the spat X35 

 times; 7, twenty -days-old spat (natural size); 10, young oyster, 2J4 to 3 

 months old. After Ryder. 



It now has a minute shell, and swims about by means 

 of two little flaps, fringed with minute, slender hair-like 

 processes called ''cilia/' It swims near the surface of the 

 ocean, and is borne about by the currents, and it is in this 



