Sand worm also known as Nereis, clam worm, rag worm. This worm mainly found on the tubular burrows in the sea shore. Nereis is the unisexual and the reproductive phase is known as heteronereis. Fertilization is occur in the sea water and during its development larva stage is called trochophore larva.

Hello.
The sandworm scientifically called as Nereis Unisexual organism.
The Unisexual organism is organisms in which male and female gonads are found in separate individual of the species.
The Nereis belongs to phylum Annelida and is dioecious and it's reproductive phase is called as "Heteronesis ". The fertilization is carried out in sea- water.

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