Receptor organs include tactile organs, taste buds, statocysts, photoreceptor cells and sometimes eyes with lenses in some.The nervous system consists of a pair of cerebral ganglia brain and double ventral nerve cord having segmentally arranged ganglia and lateral nerves in each segment.Excretion is by metamerically disposed coiled tubes nephridia which communicate the coelom to the exterior.Blood is red due to the presence of hemoglobin or erythromycin dissolved in plasma. The blood vascular system is a closed type.Respiration occurs through moist skin or gills of parapodia and head.The alimentary canal is straight tube-like, complete, extending from mouth to anus.The presence of true schizocoelous coelom usually divided into compartments by transverse septa.It may be bored by lateral fleshy appendages or parapodia. ![]() Locomotory organs are segmentally repeated chitinous bristles called setae or chaetae, embedded in the skin.The body wall is contractile or dermo-muscular consisting of outer muscle fiber circular and inner longitudinal.The epidermis is of a single layer of columnar epithelial cells, covered by thin cuticle not made of chitin. ![]()
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