Phylum Platyhelminthes, also known as flatworms are acoelomates and they include many free-living and parasitic life forms
Three body layers present in the body of flatworms are endoderm, mesoderm and ectoderm.
Endoderm is the inner lining of the gut, comprising the digestive and respiratory organs, is made up of endoderm. It is the innermost embryonic layer.
Mesoderm gives rise to muscles, blood and blood vessels, reproductive organs, organs of excretion, and muscular linings that surround many other organs including the gut. It is the middle layer that is located in between the inner layer endoderm and outermost layer ectoderm.
Ecotoderm makes up skin, shells, and other protective coverings, as well as various sensory organs and nerves. It is the outermost layer