Distinguish between the following
(a) Prostomium and peristomium
(b) Septal nephridium and pharyngeal nephridium

Explanation

(a) Prostomium is a small, fleshy lobe representing the dorsal edge of the peristomium that projects forward above the mouth whereas peritomium is a crescentic aperture at the anterior end of the first segment of earthworm. (b)