562 
OYSTER. 
timber, or sea-weeds, afford them this security ; and 
it has been asserted that, in the tropical climates, 
when the trees which grow near the mouths of 
rivers chance to bend their branches into the water, 
the oysters frequently hang to them in clusters. 
It has been long supposed that oysters have no 
ability to change theii situations; but are obliged 
for ever to remain in one place. This, however, is 
not strictly the case, as it has been ascertained that 
they possess a degree of locomotive power, and oc- 
casionally move themselves by ejecting water with 
considerable force from their shells. This peculiarity 
in oysters may be observed, says the Abbe Dic- 
quemare, by putting some of them in a plate placed 
in a horizontal position, which contains as much 
sea- water as is sufficient to cover them. 
