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

Explanation

(a) Prostomium snf paristomium .
Peristomium is first segment of earthworm and surrounds the mouth , while prostomium is a fleshy extension of peristomium and lies dorsal to mouth.
(b) Septal nephridium and pharyngeal nephridium.
septal nephridium is attached on intersegmental spetum from 15th segment onward and is with ciliated funnel so called open type, while pharyngeal nephridium is present in one of the 4th and 6th segments and lacks ciliated funnel so called closed type.