Reproduction

Free-living flatworms can reproduce either sexually or asexually. Most free-living flatworms are hermaphrodites, meaning they have both male and female organs. During sexual reproduction, the worms join in pairs. One worm delivers sperm to the other while receiving sperm from it at the same time. The eggs, which are laid in small clusters, hatch within a few weeks. Asexual reproduction by fission is common among flatworms. One form of it may be “falling to pieces”, and each piece will grow into a new worm.
Most flukes are hermaphrodites and undergo sexual reproduction in a manner similar to free-living flatworms, but they produce more eggs.
Tapeworms reproduce sexually, producing fertilized eggs in the proglottids. Mature proglottids break off the posterior end of the tapeworm and burst open, releasing thousand of eggs in the host’s intestine or the environment after passed out with feces.

Roundworms reproduce sexually. Most species of roundworms have separate males and females, but few species are hermaphroditic. Fertilization takes place inside the body of the female. Roundworms that are parasitic often have complex lifecycles that involve two or more hosts.