a tubular cell of the excretory organ (protone-phridium) of lancelets and certain annelids and nemathelminths. The head of a solenocyte, which includes the body and nucleus of the cell, becomes a long, hollow stalk or tubule that opens into the lumen of the main canal of the nephridium. One or more flagella extend from the body of a solenocyte into the tubule. The part of the tubule that is closest to the head is pierced by ultrathin slits through which fluid is sucked in by the pulsating action of the flagella.