298 
natural history 
race would soon become extinct, since this mode of pro- 
curing their living subjects them to eternal warfare. 
Oyster. ( Ostrea .) This genus comprehends the two 
extensive families of pectens or scallops, and oysters; 
and there are no less than a hundred and thirty-six spe- 
cies in the whole. In both divisions, the animal is well 
known as a nutritive and valuable food- Both scallops 
and oysters are found plentifully in the Indian Seas, the 
Mediterranean, the American ocean, and in the Euro- 
pean seas, where they constitute a considerable article of 
commerce. The scallops grow a sort of coarse byssus; 
and have the agility of leaping full half a yard out of 
the sea, at which time they open their shells, and spout 
out the stale water within them; after which they rapidly 
sink, taking in fresh water, and closing their shells with 
a loud snap, which betrays their beds to the watchful 
fisherman. 
The difference between the oyster and the scallop is 
obviously impressed by the hand of nature; but its 
movements both in the water and out are still more con- 
trary — for when left dry by the tide, by a sudden closing 
of its valves, assisted by the foot, it has the power of 
springing four or five inches at a jerk, repeating this 
motion in order to regain its element. In the water, it 
has the power of rising and sustaining itself near the 
surface, turning about in various directions^ and on any 
alarm suddenly closing the valves and sinking to the 
bottom.— The oyster, on the contrary, is unfurnished 
either with a foot or with byssus; and its powers of mo- 
tion consist only in turning either the flat or convex side 
upwards or downwards; and even to effect this, the animal 
is said to take advantage of the force of the ebbing or 
flowing of the water to assist it. 
The oyster excludes its young completely formed; and 
by the help of a magnifier, the joinings of the little infant 
shells can be distinctly seen, with all their parts as per- 
fect as the parent animal, though appearing to the naked 
eye only as a minute point. 
