Annelidan Characters:-

1. Vermiform body with truncated extemities.
2. True head is absent.
3. Segmentation in both seems to be homonymous.
4. Outer body is covered by cuticle, skin usually thin and flexible.
5. Muscles are smooth and muscles function in an identical way.
6. Hollow appendages are seen with unjointed character.
7. Locomotion functionalise by peristalsis similar to earthworms.
8. Alimentary canal is simple and straight fixed.
9. Nephridia are paired and present segmental.
10. Slime glands and coxal glands activate with similar chaetopoda's glands.
11. Structure of eye alike polychaetes.
12. Reproduction tracts are full of cilia.

Arthropodan Characters:-

1. Antennae is present.
2. Chitinous cuticle found on the body similar to arthropods.
3. The appendages are present with claws.
4. Jaws are variated in appendages.
5. Locomotion by legs.
6. Haemocoel is present.
7. Coelom reduced to the excretory's cavities and reproductive parts.
8. Peculiar salivary glands, may be defined to be modified nephridia.
9. Lateral Ostia as doors between heart and pericardial sinus.
10. Respiratory organs are present in the form of Trachea.
11. Perivisceral part of coelom is absent.
12. Brain is large and functions as in typical arthropods.

Structure of reproductive organs and the pattern of development is similar to arthropods.

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