NEPHRIDIUM

Noun

nephridium (plural nephridia)

(biology) a tubular excretory organ in some invertebrates

(anatomy) the embryonic excretory organ that develops into the kidney

Source: Wiktionary

Ne*phrid"i*um, n.; pl. Nephridia. Etym: [NL., fr. gr. kidneys.] (Zoöl. & Anat.)

Definition: A segmental tubule; one of the tubules of the primitive urinogenital organs; a segmental organ. See Illust. under Loeven's larva.

Source: Webster’s Unabridged Dictionary 1913 Edition