Earthworm - Morphology And Anatomy

The earthworm body is metamerically segmented, and NCERT describes specific external markers that help identify regions of Pheretima. A prominent dark band of glandular tissue, the clitellum, covers segments 14, 15 and 16, dividing the body conveniently into a preclitellar, clitellar and postclitellar region. The clitellum secretes the material that forms the cocoon in which fertilised eggs develop, making its position a key identification feature. Segments 5 to 7 lie in the preclitellar region and do not carry the band. Segments 20 to 22 belong to the postclitellar region and bear no clitellum. Segments 9 to 11 contain the openings of the spermathecae and other reproductive structures but are still anterior to the glandular girdle. As stated in NCERT Class 11, Chapter 7 (Structural Organisation in Animals), the clitellum of Pheretima occupies segments 14–16. An anatomical order check confirms that the band must lie between the spermathecal segments anteriorly and the bulk of the postclitellar body posteriorly, consistent only with segments 14 to 16.