Definitions for "Protonephridia"
excretory tubules that are ciliated at one end and closed at the other.(empty) reduction division: The production of gametes with half the chromosomal complement of the original cell; sexual reproduction. rhizome: An underground stem that tends to grow parallel to the surface. secondary growth: Increase in the diameter of stems and roots of many plants, particularly "dicots". sorus (pl. = sori): A collection sporangia or spores, as is often found on the underside of fern fronds. sporophyll: Spore-producing leaves that bear sporangia and are specialized for reproduction. sporophyte: The diploid (2n) stage of an organism that possesses alternation of generations in which hapoid (1n) spores are produced. stolon: A stem that grows along the surface of the ground.
Singular: protonephridium. A primitive osmoregulatory or excretory organ made up of a tubule ending at a flame bulb, or solenocyte.
Keywords:  flatworms, nef, rid, toe, maintain
pro-toe-nef-RID-ee-a Structures in flatworms that help maintain internal water balance. 518