Platyhelminthes are a type of animal with a flat body. Its main characteristics include:
1. Flat body: The body of flatworms is flat and usually consists of only two layers of cells, with epidermal cells both inside and outside.
2. No body cavity: Unlike other animals, platyhelminthes do not have a true body cavity, but have a structure called a "funnel cavity" through which physiological functions such as respiration and excretion are carried out.
3. Ganglia: Platyhelminthes have some ganglia distributed at the front and center of the body, which can control sensation and movement.
4. Single-hole digestive system: Platyhelminthes have only one mouth and no anus. Food will be digested and absorbed after entering, and waste produced in the body will be excreted from the mouth.
5. Diverse reproduction methods: Platyhelminthes have various reproduction methods, including selfing, outcrossing, schizophrenia, spores, etc.
In short, platyhelminthes have flat bodies, no real body cavity, and a single-hole digestive system, making them unique in both morphology and physiology.
