Rhabditophora
Rhabditophora (from "rhabdito"-, rhabdite + Greek -φορος [-"phoros"], bearer, i.e., "rhabdite bearers") is a class of flatworms. It includes all parasitic flatworms (clade Neodermata) and most free-living species that were previously grouped in the now obsolete class Turbellaria. Therefore, it contains most of the species in the phylum Platyhelminthes, excluding only the catenulids, to which they appear to be the sister group. The clade Rhabditophora was originally erected by Ulrich Ehlers in 1985 based on morphological analyses and its monophyly was later confirmed by molecular studies. Description. Rhabditophorans are characterized by the presence of lamellated rhabdites, rodlike granules  secreted in the cells of the epidermis and consisted of concentric lamellae. They are absent in the clade Neodermata, most likely due to a secondary loss of this feature because their epidermis is turned into a syncytium in adult forms. Another important synapomorphy of the group is the duo-glandular adhesive system. It is a structure of the epidermis containing three different cell types: anchor cells, adhesive glands and releasing glands. The adhesive glands secrete an adhesive substance that attaches the anchor cells to a surface, while the releasing glands secrete a substance able to release the anchor cells from  surfaces. This systems allows rhabditophorans to adhere and release quickly from the substrate, even several times in a second. The secretory organs of rhabditophorans, the protonephridia, also have a unique anatomy in which the flame cells and tube cells present a series of cytoplasmic projections that overlap, forming a two-cell 'weir'. Systematics. The following orders are recognised in the subphylum Rhabditophora: