Platyhelminthes meaning "Flatworm"
Planeria
Planeria have both male and female reproductive organs, and can sexually reproduce or asexually reproduce. It can either fertilize it's own egg and give birth to those eggs later, or detach a piece of itself from its body and let adult stem cells do the work of creating a new planeria. These adult stem cells are called neoblasts and divide and differentiate the cells of the small piece of the original organism so it can grow and develop. However, among the Planeria sexually reproduction is most desired due to the results of the offspring. It allows the species to thrive and evolve due to the genetic variation that comes from sexually reproduction. It is also less risky then asexual reproduction.
Divided Flatworm
This flatworm, like the other members of the Platyhelminthes phylum, is a hemaphrodite. This means that it bears both male and female reproductive organs. It can go through the process of either asexual or sexual reproduction. Since it has both gender's reproductive organs it doesn't need a partner to undergo sexual reproduction with. It can also go through asexual reproduction by removing a small piece of it's body from itself and letting that piece grow into an individual flatworm again. This ability to regenarate very quickly gives the members of the Platyhelminthes phylum skilled qualities in being parasites. The reason most flatworms choose to reproduce sexually is becuase it is quicker, safer, and allows the species to evolve faster by having more genetic variation then that of asexual reproduction.
Tapeworm
Tapeworms are interesting because they have the ability to reproduce both sexually and asexually. Mature tapeworms contain both male and female reproductive organs. Sperm from the tapeworm will either fertilize it's own egg, or find another egg to fertilize amongst the other tapeworms. Once the egg is fertilized it will pass through the fecal metter of the host until it finds another host. Once inside the new host the tapeworm will then burrow itself inside and repeat this process over and over again. The tapeworm is a parasite and relies on a host in order to live and reproduce. It is covered in either hooks or other tools used to attach itself onto a new host.