It is an extra bit to something. For example: The appendix is an appendage to the bowel. Your arms are an appendage to your body.
appendages are how many body parts do they have
It is any structure attached to a part of the body of an organism. :)
A platyhelminthe is a flatworm.
Platyhelminthes breathe using their entire body. Being flat, oxygen diffuses quickly across the skin and to all parts of the body, so they don't need a blood circulatory or respiratory system.