The clitellum is a distinct part in the body of earthworm, it is found in

1.  segment 13-14-15

2.  segment 14-15-16

3.  segment 12-13-14

4.  segment 15-16-17

 

 
(b) The clitellum is a Prominent circular band of glandular nature, present in 14th to 16th Segments in earthworm. Clitellum secretes mucus and albumin, which helps in the formation of cocoons, and is used for fertilisation of eggs.