Formation of cocoon in earthworm, Biology

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Formation of cocoon in earthworm:

In earthworm segments from 14 to 17 are swollen. Skin on these segments is thick and glandular. This is called clitellum.
When ovaries mature, the clitellum secretes a viscous substance in the form of a girdle.
This girdle hardens into a cocoon around the clitellum.
Earthworm wriggles out of the cocoon - cocoon moves anteriorly and the worm moves posteriorly.
Ova are discharged into the cocoon. When the cocoon moves over the spermathecae openings. Spermatozoa received from another animal are stored in the spermathecae are discharged into it.
The cocoon finally comes out of the body and both ends of cocoon get closed.
Fertilization takes place in cocoon. Since fertilization is taking place outside the body, it is external fertilization.
After about 8 to 10 weeks, young earthworms come out of the cocoon.

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