nephridium

Genital funnel. h, “Head kidney,” with second nephridium just below it. i, Intestine. l.m,

In the male there are a right and a left protrusible penis in every genital segment, into which opens the nephridium and a sperm-sac.

Male pore. n, Nephridium. o.m,

Near this and less advanced into the branchial chamber is the single renal organ or nephridium r with its opening to the exterior r′.

The connexion with the pericardium of the smaller of the two renal organs was demonstrated by Lankester in 1867, at a time when the fact that the renal organ of the Mollusca, as a rule, opens into the pericardium, and is therefore a typical nephridium, was not known.