The integument of a Polychaetous anellid (Ophryotrocha) is a pseudo-stratified columnar epithelium lying on a very thin basement membrane and covered by a schlerotized proteic cuticle. The cuticle is present in ciliated regions and is lacking onlyat the pores of the mature dermal glands. The epithelium is formed by covering and glandular cells. The septal zones of each metamere and the parapodia are lined by cubic covering cells, thoug the interseptal zones of the metamere have scattered and tall covering cells. Around the equator of each metamere one row of large cells, bearing cilia, is present (three rows are around the head). Vesicular cells are growing from the septal to the interseptal zone of each metamere, and during the animal growth became more and more frequent near the ciliar rows. These cells are olocrine muciparous glands. The caudal metamera of some grown animals may have two lateral groups of club-shaped cells secreting an acid glycoprotein. The source of new epithelial cells is found in the covering cells surrounding the septal zones of the metamera.