Phylum :- Annelida
(ii) The body cavity is true coelom, which is lined by a peritoneum or coelomic epithelium & serves as a hydrostastic skeleton against which muscles can contrast.
(iii) Body cavity often subdivided by transverse septa.
(iv) Presence of muscular gut with mouth & anus.
( v) Closed blood circulatory system.
Class :- Polychaeta
(ii) Distinct head bearing eyes,tentacles,cirri & palps.
(iii) Pharynx with or without jaws or teeth.
(iv) Presence of numerous chaetae or bristles, inserted in two groups in the biramous segmental parapodia.
Examples :- Nereis; Aphrodite; Chaetopterus; Sabella;
|Fig :- Chaetopterus|
Class :- Oligochaeta
(ii) Body segment lack parapodia but have setal sacs from which setae as group of bundle.
(iii) Presence of clitellum.
(iv) Hermaphrodites with distinct gonads restricted usually to a few anterior segments.
Examples :- Pheretima; Lumbricus; Tubifex; Megascolex;
|Fig :- Megascolex|
Class :- Hirudinaria
(ii) Usually two suckers are present a powerful posterior sucker & small anterior or head sucker surrounding the mouth.
(iii) Tentacles, parapodia & setae are absent.
(iv) Coelom much reduced & filled by connectives tissues.
Examples :- Hirudinaria; Hirudo; Acanthobdella;
|Fig :- Acanthobdella|