1. The sixth abdominal ganglion (6 A.G.) of the lobsterHomarus gammarus(L.) innervates the rectum via the paired posterior intestinal nerves (P.I.N.’s) and the paired anal nerves. The anterior branches of the P.I.N.’s supply the anterior hindgut, the main faecal expulsion region, whilst the posterior branches (P.I.N.p.’s) supply the posterior region and the 5 extrinsic radial muscle groups around the anus.