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This paper resumes the first electron microscopy investigation regarding the classes Synurophyceae and Chrysophyceae in Madagascar. 42 taxa (38 new to the country) of the genera Synura, Chrysodidymus, Mallomonas, Chrysosphaerella, Spiniferomonas and Paraphysomonas are illustrated and the morphology of their silica structures examined. Biogeographical problems are discussed, especially emphasizing differences between the 12 regions, here representing the country. While the central plateau has a largely cosmopolitan species composition, the coastal and lowland floras have many tropical components. The SW coast and the island Nosy Be are both species poor.

Two species of amoebae, capable of living and multiplying in the absence of oxygen, were isolated from anaerobic marine sediments. Vahlkampfia anaerobica does not have typical mitochondria (but has organelles covered by a double membrane) and it harbours endocytic bacteria. The nuclear envelope of V. anaerobica is associated with the cisternae of the rough endoplasmic reticulum which is a remarkable feature of this species. Vannella peregrinia has double membraned organelles with internal tubular structures, which morphologically resemble mitochondria. Its cell coat consists of glycostyles, which differ in dimensions from those of other Vannella spp.; it needs further investigation.

A revision of the genus Raphidiophrys ARCHER on the basis of the scale structure is performed. Two new genera are proposed. Parasphaerastrum gen. nov. includes a single species, P. marina (OSTENFELD) emend. MIKRJUKOV, surrounded by the envelope of rod-like tangential siliceous spicules. Polyplacocystis gen. nov. includes five species, two with reticulate [P. ambigua (PENARD) and P. symmetrica (PENARD)] and three with smooth [P. pallida (SCHULZE), P. marginata (SIEMENSMA) and P. pedunculata (MIKRJUKOV)] surface of scales. Six other EM-studied species [R. capitata SIEMENSMA et ROIJACKERS, R. elegans HERTWIG et LESSER, R. intermedia PENARD, R. minuta NICHOLLS, R. Viridis ARCHER and R. ovalis (Dü;RRSCHMIDT)], which have complex scales formed by two parallel plates and internal septae between them, are retained in the genus Raphidiophrys ARCHER. Only three species with plate-scales identical to those in Polyplacocystis (R. lemani PENARD, R. tubifera PENARD, and R. glabra NICHOLLS et 0üRRSCHMIDT) stay in the genus Raphidocystis with the emended diagnosis given by NICHOLLS & DüRRSCHMIDT (1985). The new family Raphidiophryidae is proposed including the genera Parasphaerastrum, Polyplacocystis, Raphidiophrys and Raphidocystis. A key for the species of these genera is proposed.

The morphology and infraciliature of Trachelocerca sagitta (MÜLLER, 1786) EHRENBERG, 1840, Tditis (WRIGHT, 1982) novcomb., Tracheloraphis phoenicopterus (COHN, 1866) DRAGESCO, 1960, Taragoi (DRAGESCO, 1954) DRAGESCO, 1960, Tlongicollis (DRAGESCO, 1960) novcomb., and Toligostriata (RAIKOV, 1962) novcombwere studied in live and protargol impregnated specimens, as well as with the scanning electron microscopeNeotype slides with protargol impregnated specimens of each species have been deposited in (LI)The somatic and oral infraciliature of the species investigated basically agrees with that of Trachelolophos and PrototrachelocercaSpecifically, all have a glabrous stripe bordered by a peculiar (bristle) kinety composed of dikinetids having a unique ciliation and flbrillar systemFurthermore, all trachelocercids have specialized structures at the anterior end of the body, highly reminiscent of a prostome and/or gymnostome oral apparatusSome of the species investigated represent the types of the genera Trachelocerca EHRENBERG, 1840 (Tsagitta), Tracheloraphis DRAGESCO,1960 (Tphoenicopterus), and Trachelonema DRAGESCO, 1960 (Tlongicollis), three taxa often confused due to the vague original diagnosesOur study provides accurate characteristics for distinguishing Tracheloraphis (with brosse) from Trachelocerca (without brosse), while the genus Trachelonema is synonymized with Tracheloraphis because of distinct similarities in the infraciliatures of the type speciesAccordingly, three well-defined genera are recognized in the family Trachelocercidae KENT, 1881: Trachelocerca EHRENBERG, 1840, Tracheloraphis DRAGESCO, 1960, and Trachelolophos FOISSNER & DRAGESCO, 1996The order Trachelocercida JANKOWSKI, 1978 is redefined using the glabrous stripe, the bristle kinety, and the apical location of the oral apparatus as unique character constellationHENNIG's cladistic method suggests that the Trachelocercidae evolved from the Prototrachelocercidae and both have a common ancestor with the LoxodidaSome minor taxonomic changes (new combinations) and many nomenclatural emendations have been made.

Three pigmented flagellates: Gloeomonas mamillosa, Lobomonas tubulata (Chlamydomonadales, Chlorophyceae) and Strombomonas quadrangularis (Euglenales, Euglenophyceae) are described as new taxa from material collected in two freshwater bodies located in the Municipality of Rio de Janeiro, Rio de Janeiro State, southeastern Brazil.

The biodiversity of five shallow freshwater and slightly brackish ponds (North East Greenland; 79-81 ° N) has been studied with particular emphasis on taxonomical and ecological aspects of loricate and scale-covered forms, i.echoanoflagellates, chrysophytes and heliozoansThe material was collected in July 1993 as part of the IAAP Northeast Water (NEW) Polynya programme and represents the northernmost freshwater and brackish localities analyzed using electron microscopical techniquesMorphometric data and physical, chemical and biological parameters (pH, temperature, salinity, nutrients, chlorophyll-á) are provided for all ponds sampledThe light- and electron microscopical examination of samples revealed 2 choanoflagellates, 14 chrysophytes and 7 heliozoan taxaSeven species are recorded from Greenland for the first time and two species are considered new to science, vizEpipyxis thamnoides and Pseudokephyrion poculiformeA crucial difference was observed on the one hand between the single land pond (location 33) characterized by high diversity and high biomass, and on the other the glacier and the ice floe melt ponds characterized by low diversity and low biomassBiogeographically the community sampled displays significant similarities with localities previously investigated within the Greenland and northern Canadian region.

Pseudaphelidium drebesii genet specnovis a parasite of the centric marine diatom Thalassiosira punctigeraThe motile stage consists of a zoospore with a single opisthokont flagellumIt attaches to a host cell, encysts, penetrates the frustule and develops into a plasmodiumThe plasmodium phagocytizes portions of host cytoplasm which are included in a single big digestion vacuoleAt the end of the trophic phase the plasmodium is a hollow sphere filling the frustule completelyIt cleaves to form ameboid cells which are slowly motile and finally encystThe cysts release 4, sometimes less, zoosporesDiagnoses of genus and species are given, and the uncertain taxonomic position of Pseudaphelidium is discussed.

Four new Myxobolus species are described from cyprinid fishes of the Mesopotamian Fauna Region in IranEach species infects a specific site of their fish hostsMyxobolus iranicus spnforms large plasmodia in the spleen of Barbus sharpeyi and Bluteus. The plasmodia of Mmesopotamiae spnare located in the fins of Bgrypus, Bluteus and BrajanorumThe plasmodia of Mshadganispndevelop on the cartilageous rays of the gill filament in Brajanorum, while Msharpeyi spnforms plasmodia inside the cartilageous gill arches of Bsharpeyi.

A revision of the centroheliozoan family Heterophryidae on the base of the external envelope structure is performedThe genus Cienkowskya is shown to have no centroheliozoan affinities and is transferred from this group; it is a heliozoa incertae sedisThe genus Heterophrys is shown to be heterogeneousHfockii with a tangential orientation of organic spicules is transferred to the genus Sphaerastrum GREEFF, emend., while the other species with radial spicules remain in the genus HeterophrysA new species Hfebvre-chevalierae is describedEmended diagnoses for genera Heterophrys and Sphaerastrum and species Hmyriopoda, Hmarina and Sfockii and a key for the family Heterophryidae are suggested.