ULTRASTRUCTURE OF THE EPIDERMIS AND PROTONEPHRIDIUM OF AN UNDESCRIBEDSPECIES OF LURIDAE (PLATYHELMINTHES, RHABDOCOELA)

The epidermis of an undescribed species of Luridae possesses many larg e cavities filled with a medium-dense material, intraepidermal nuclei, glandular ducts, cilia with vertical and horizontal rootlets, surface microvilli, and a thick basal lamina. Cilia have narrow tips, the per ipheral axonemal doublets lose one of the microtubules and, finally, w hole doublets are lost near the tip. Flame bulbs have a single row of longitudinal ribs containing microtubules and connected by a 'membrane ' apparently of extracellular matrix; cilia of flame bulbs possess cro ss-striated rootlets, and capillary walls are smooth. The nucleus of t he protonephridium was observed near the tip of the flame bulb, along the capillary. It is not clear whether one perikaryon forms more than one flame bulb. The structure of the epidermal ciliary rootlets, the p resence of intraepidermal nuclei, and flame bulbs composed of a single row of longitudinal ribs containing microtubules formed by a single c ell are typical rhabdocoel characteristics.