Source : Webster's Revised Unabridged Dictionary (1913)

Nephridium \Ne*phrid"i*um\, n.; pl. {Nephridia}. [NL., fr. gr. ?
   of the kidneys.] (Zo["o]l. & Anat.)
   A segmental tubule; one of the tubules of the primitive
   urinogenital organs; a segmental organ. See Illust. under
   {Loeven's larva}.

Source : WordNet®

nephridia
     See {nephridium}