Phylum Platyhelminthes includes the flatworms which shows the following characters.

• Multicellular organisms with organ grade of organisation. 
• The body is bilaterally symmetrical and dorsoventrally flattened. 
• The body wall is triploblastic with ectoderm, mesoderm and endoderm forming the layers. Coelom is totally absent.
• The body is unsegmented and varies in shape. It may be elongated, flattened, ribbon like or leaf-like. 
• The parasitic forms are protected by a thick cuticle and bears, hooks, spines or suckers for attachment.
• Digestive, circulatory, respiratory and skeletal systems are absent. 
•  Excretion occurs by excretory cells called flame cells which form the protonephridia.
• Nervous system consists of nerve aggregations called ganglia.
• Sexes are mostly united (Hermaphrodites). Reproduction is by asexual and sexual methods. Development is indirect.

Class – Turbellaria Eg. lanaria

Class – Trematoda Eg. Fasciola hepatica

Class – Cestoda Eg. Taenia solium