These animals are segmented into segments called metameres. In fact, each segment contains units of circulatory, nervous, and excretory systems. They are covered by a moist outer cuticle. These organisms acquire a closed circulatory system that is segmentally arranged. They have a one-way digestive tract with separate mouths and anus. They breath through the moist skin. Both circular and lengthwise muscle fibers sllow their great flexibility and movement.
