Order Acoela Exclusively marine; mouth present; pharynx simple or lacking; no intestine; without protonephridia, oviducts, yolk glands, or definitely delimited gonads; about 200 species. Order Neorhabdocoela Saclike linear intestine; protonephridia and oviducts usually present; gonads few, mostly compact; nervous system generally with 2 longitudinal
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