Food tube simple. Mouth at anterioventral and anus terminal. Pharynx sometimes eversible with jaws. Dorsal and ventral major vessels connected by segmented connections that may act as hearts. Some have respiratory pigments dissolved in plasma.
Animals move by differential hydrostatic pressure in the segments in concert with the setae.
Dioecious or hermaphroditic. Fertilization external or internal. B Taxonomy of the Phylum. Aphrodite, Manayunkia, Glycera, Chaetopteris, Arenicola, Amphitrite, Polygordius, Nereis, Nephtys. Aeolosomatans resemble interstitial polychaetes in some respects and oligochaetes in others.