At
a very moderate estimation, the total number of three to six year old
oysters which lie upon our beds will produce three hundred billions of
eggs. This number added to that produced by the five millions of full
grown oysters would give for every square meter of surface not merely
1,351 young oysters, but at least 1,535. In order to determine how
many eggs oysters produce, they must be examined during their spawning
season. This begins upon the Schleswig-Holstein beds in the middle of
June, and lasts until the end of August or beginning of September. The
spawning oyster does not allow its ripe eggs to fall into the water, as
do many other mollusks, but retains them in the so-called beard, the
mantle, and gill-plates until they become little swimming animals. The
eggs are white, and cover the mantle and gill-plates as a semi-fluid,
cream-like mass. As soon as they leave the generative organs the
development of the germ begins. The entire yolk-mass of the egg divides
into cells, and these cells form a hollow, sphere-like body, in which an
intestinal canal arises by the invagination of one side.
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