The size of roundworms ranges from microscopic to as long as 3.3 feet (1 meter). Most roundworms have a hard, sharp spear on their head, and some have bristles on the head. The body of roundworms is protected by a flexible but strong, grooved body covering. A layer beneath this covering releases fluids that harden to form the covering. The body has three tissue layers and a fluid-filled false body cavity, meaning the cavity is between the inner and middle layers rather than the middle layer and the outer layer, as it is in complex animals. The sensing system of roundworms is made up of holes behind, or in some cases on, the lips.
Animal Life ResourceJellyfish, Sponges, and Other Simple AnimalsRoundworms: Adenophorea - Physical Characteristics, Roundworms And People, No Common Name (desmoscolex Squamosus): Species Accounts, No Common Name (mermis Nigrescens): Species Accounts - GEOGRAPHIC RANGE, HABITAT, DIET, BEHAVIOR AND REPRODUCTION, CONSERV