| THE OYSTER AND OYSTER-CULTURE. 691 
lie within an area 74 kilometers long by 22 broad, yet the nature of the 
oysters, and especially the form and solidity of the shell and the flavor 
of the animal, differ very greatly. Upon two beds inside of the south 
point of the island of Sylt are found oysters which in fullness and deli- 
cacy of flavor are not inferior to the best English “natives.” 
Fic. 4. 
A full-grown Schleswig-Holstein oyster, about ten years of age. It is a female with 
eggs, and was drawn from life, on the 14th of June, 1871, by Mr. J. Wittmaack. The 
right, or upper, valve of the shell has been removed. The oyster lies in the hollow 
of the left valve, in its natural position. On the upper side the thickened layers of 
the shell can be seen. Each year new shell-layers are formed. The inner surface of 
the shell is white to near the edge, where it becomes of a brownish color. Above, 
close to the back of the animal, which issomewhat curved, is a crescent-shaped brown 
mass, the shell band or ligament. In separating the valves this band is broken across 
in the middle. The right side of the animal is exposed to view; the left rests upon 
the inner hollow surface of the left valve. The upper layer, with its edge turned 
back, is the mantle-lobe or fold of the right side. The white lines seen in it are mus- 
cular fibers. The left mantle-lobe lies close upon the shell, and is more expanded than 
the right. The gills are to be seen just below the inverted edge of the right mantle- 
lobe. In the oyster they are four in number. The outer gill of the right side is the 
most exposed; a narrow border of two others can be seen. All four have furrows run- 
ning from the inside to the edges. Upon these furrows are sithated cilia, by the mo- 
tion of which water is driven over the gills for the purposes of respiration. Along the 
