J.B.Lamarck(1809) introduced the word Annelida for the segmented worms.Annelida is a eucoelomate and schizocoelomate phylum of the division Protostomia and the grade Bilateria.The animals included in this phylum are world wide in distribution with about 8670 species.
Distinct cephalization,true metamerism schizocoelom,closed blood vascular system,nephridiafor the excretion,setae for locomotion,a well-differentiated muscular digestive system etc.are some of the important characters of this phylum.
The phylum Annelida includes three classes namely Polychaeta,Oligochaeta andhirudinea representing the bristle worms,the earth worms and the leches respectively.class archiannelida,which was included under this phylum,is treated as a separate phylum at present.
chaetogaster annandelei is the smallest earthworm,while Megascolides australis is the longest earthworm.dravida grandis inhabiting southIndia is the longest earhwormin India.40 species of earthworms are reported from India.Pheritima posthuma is the common Indian earthworm.
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