Ultrastructural observations of the lappets of the adult and metacercarial stage of Diplostomum phoxiniFaust, 1918, indicate that the tegument is specialised in this region, possesses finger-like processes and receives the ducts of secretory glands. The glands are unicellular with the nucleated portion lying in the fore-body and possess long necks, supported by microtubules, which discharge at the surface of the tegument. Two types of gland cell are present: type A which produces large secretion bodies with homogeneous contents and type B producing egg-shaped bodies with a core of lightly staining material and dense apical and peripheral regions. The extrusion pattern is holocrine and in the ‘mature’ gland cell the cytoplasm becomes completely replaced by secretion. The lappets and both types of gland cell are fully formed at the ‘mature’ metacercarial stage.