platyhelminthes
Platyhelminthes, also latin for flat worms, are flat worm animals who digestive system is bilaterally symmetrical, so both the left and the right sides are symmetrical. These flat worm animals also have a gastrovascular cavity as their stomach, with a mouth that also acts as an anus.
tapeworm
The Tape Worm or Cestoda is a Platyhelminthes that hosts itself onto other organisms. It is a parasite that has no digestive system absorbs all of its nutrients from the inside of the hosts gut. The Tape Worm losses its own digestive system and attaches to the hosts using its scolex. While attached it continues to eat from the host, and get bigger overtime.
Planaria
The Planaria of the Turbellaria class is one member of the platyhelminthes phylum that is not a parasite. The Planaria has a mouth, a pharynx and a gastrovascular cavity. the mouth is under the belly of the creature, and it secretes digestive enzymes to begin external digestion. The Pharynx connects the mouth to the gastrovascular cavity. Nutrients diffuse throughout the body, and waste is execrated throughout the top dorsal of the Planaria.
Schistosoma mansonii ( blood fluke).
The Schistosoma mansonii or blood fluke is a flatworm parasite. This parasite also has a bilateral symmetry and oral and ventral suckers to absorb nutrients from its host. It has a blind ending digestive system with a stomach caeca and a oesophagus. After absorbing nutrients from its hosts blood, it then excretes the waste through its flame cells.