The various kinds of buccal organ recognised by Rouse and Fauchald (1997) are here mapped onto the same tree that was used to develop their new classifciation of polychaetes. In this transformation a simple ventral buccal organ represents the primitive condition for polychaetes and subsequently transforms into the other kinds of buccal organs. The loss of a buccal organ appears to have occurred twice from the ventral buccal organ, once for Sabellida witht he likely subsequent loss of all gut openings in Siboglinidae which have symbiotic bacteria in the endoderm. The second loss is with Chaetopteridae which show an elaborate filter-feeding mechanism.