The Third International Symposium, The Biol technical papers by subject matter and to preface ogy of the Turbellaria', was held at the Limburgs each group where possible by one or two of the Universitair Centrum, Diepenbeek, Belgium from invited review papers covering the same field: We II to 15 August 1980. The first (Chicago, 1970) and hoped in this way to make the published pro second (Helsinki, 1977) symposia were held in ceedings more unified and more useful as a general memory of Libbie Hyman and Alex Luther respec overview of turbellarian biology. tively. This third symposium, however, was held in The success of the symposium was in no small honour of a living legend within the field of way due to the splendid facilities which were made turbellarian biology, Tor G. Karling. The co available by the Limburgs Universitair Centrum, organizers of the symposium took special pride in and in acknowledging this help we must make this, not only for its acknowledgement of Tor special mention of the Rector, Professor Dr. L. Karling's scientific contributions, but also because Verhaegen and the Vice Rector, Professor Dr. M.

Inhalt
50 years of turbellarian research. A brief biography of Tor G. Karling.- Systematics & Zoogeography.- The phyletic status of the Paludicola.- The geographical and bathymetrical distribution of the Fecampiidae (Turbellaria, Rhabdocoela).- The taxonomy, zoogeography and biology of Bipalium kewense Moseley, 1878 (Tricladida, Terricola).- A new species of freshwater turbellarian from Africa, predatory on mosquitoes: Mesostoma zariae n. sp. (Typhloplanoida).- Paravortex karlingi sp. no v. from Cerastoderma edule L., in Britain.- Karyological observations on Polyclads.- The karyotypes of Dugesia species from Spain (Turbellaria, Tricladida).- Karyological and taxonomic studies of Dugesia japonica Ichikawa et Kawakatsu in the Far East.- Studies on the speciation of the Japanese freshwater planarian Polycelis auriculata based on the analysis of its karyotypes and constitutive proteins.- Studies on the speciation of the European freshwater planarians Polycelis nigra and Polycelis tenuis based on the analysis of enzyme variation by means of isoelectric focusing.- Ecology & Faunistics.- The ecology of the Turbellaria with special reference to the freshwater triclads.- A comparative study of the food niches of lake-dwelling triclads and leeches.- Oxygen availability, redox and the distribution of some Turbellaria Schizorhynchidae and other forms.- Sand dwelling Turbellaria from the Netherlands Delta area.- Notes on the biology of some psammophile Turbellaria of the Black Sea.- On some commensal Turbellaria of the Canadian East Coast.- New England Coelogynoporidae.- Nutrition & Reproduction.- Physiological adaptations to entosymbiosis in three species of graffillid rhabdocoels.- The diet of three species of umagillid neorhabdocoel turbellarians inhabiting the intestine of echinoids.-Reproductive biology of Dugesia sanchezi, a fresh-water planarian from Chile.- Contrasting power of the factors for fission and sexuality in a polyploid planarian.- The embryological development of Turbellaria Kalyptorhyncia (Rhabdocoela).- Regeneration & Differentiation.- The problem of cell totipotency, dedifferentiation and transdifferentiation in Turbellaria.- Quantitative analysis of cell types during growth, degrowth and regeneration in the planarians Dugesia mediterranea and Dugesia tigrina.- Relationship between variations of cAMP, neuromediators and the stimulation of nucleic acid synthesis during planarian (Polycelis tenuis) regeneration.- Cell activation during regeneration of planarians.- Adenylate cyclase in regenerating tissues of the planarian Dugesia lugubris (O. Schmidt).- Ultrastructure.- Morphology of the Turbellaria at the ultrastructural level.- Development of cilia in embryos of the turbellarian Macrostomum.- The system of epidermal ciliary rootlets in Turbellaria.- Ultrastructure of the epidermis of adult and embryonic Paravortex species (Turbellaria, Eulecithophora).- Ultrastructural observations on paracnids. I: Coelogynopora axi Sopott (Turbellaria, Proseriata).- Fine-structural observations on the central parenchyma in Convoluta sp.- The ultrastructure of the eyes in larval and adult polyclads (Turbellaria).- Ultrastructure of the eye of Urastoma cyprinae (Turbellaria, Alloeocoela).- Observations on the ultrastructure of the copulatory organ of Archilopsis unipunctata (Fabricius, 1826) (Proseriata, Monocelididae).- Fine structure of the giant aflagellate spermatozoon in Pseudostomum quadrioculatum (Leuckart) (Platyhelminthes, Prolecithophora).- Index Auctorum.