from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A membrane-bound organelle found in certain protists that pumps fluid in a cyclical manner from within the cell to the outside by alternately filling and then contracting to release its contents at various points on the surface of the cell. It functions in maintaining osmotic equilibrium.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A vacuole that removes waste or excess water.
from the GNU version of the Collaborative International Dictionary of English
- adj. a pulsating cavity in the interior of a protozoan, supposed to be excretory in function. There may be one, two, or more.
- n. See under Contractile, and see Illusts. of Infusoria, and Lobosa.
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