Examples of representing beings: earthworms, leeches, lugworms. Basic morphology: cylindrical body, segmented (metameric). Type of symmetry: bilateral. Germ layers and coelom: triploblastics, coelomates.
Digestive system: complete. Respiratory system: cutaneous or branchial. Circulatory system: closed, with hemoglobin. Excretory system: a pair of metanephridia in each metamere. Nervous system: neural chords, a pair of ganglia per metamere, anterior concentration of neurons (primitive brain). Types of reproduction: **, with dioecious and monoecious beings.
