Structural differences of microtriches and distal cytoplasm of the tegument in the apical and lateral suckers, scolex proper and neck of Proteocephalus macrocephalus (Creplin,1815) were studied. The microthrix border in the apical sucker is formed by filamentous microtriches only. The frontal and lateral parts of scolex bear mainly filamentous microtriches, but seldom short conoid types occur. The transitional zone between scolex and neck is covered mainly with short conoid microtriches. The neck bears blade-like microtriches. In the apical and lateral suckers, the basal plasma membrane of the distal cytoplasm adheres to the basal lamina at some points only, forming thus a lacunal system at the base of the sucker tegument. In the scolex proper and neck region, the basal plasma membrane of the tegument is connected continuously with the basal lamina. The distal cytoplasm is penetrated by two types of gland cell ducts and cibate sensory receptors. Possible functions of different parts of the microthrix border are discussed.
Ultrastructure of the primitive epithelium of Echinostoma revolutum (Digenea: Echinostomatidae) cercaria was studied. The germinal balls and developing cercariae are covered with the primitive epithelium in daughter rediae. When the definitive tegument of the cercaria is differentiated, the primitive epithelium degenerates. The last remnants of the primitive epithelium in a cercaria can be detected at the stage when the lateral gland cells have released their secretion into the definitive tegument.