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Sporozoites excysted from oocysts of Isospora bigemina, I. felis and I. rivolta were inoculated to various tissue cultures to obtain endogenous development. Sporozoites of all the three species were seen to invade the cultured cells, with I. bigemina being the only species to undergo a further development. The most striking feature of the development was a keen resemblance between the growing parasite and the stages of vegetative phase of the Toxoplasma life cycle (see the figures) followed usually both in culture and in inner organs of infected animals. Serological tests (RCF) were applied to mice fed on the parasitic material from the culture with negative results within 7 days after the infection. The present findings suggest a closeness between Isospora and Toxoplasma which is in agreement with the recent discoveries of the whole life cycle of T. gondii.

Leishmania adleri Heisch is the only known species of leishmanias of reptiles pathogenic for mammals. Successive passage of the strain of L. adleri through golden hamsters causes a sharp increase in its virulence (at low initial indices). The application of immunoferritinous method for submicroscopic studies reveals great antigenic differences between this species and agents of leishmaniases of man. L. adleri differs as well from non-pathogenic leptomonads of turkmenian reptiles. In antigenic respect L. adleri is more allied to Leishmania of mammals than non-pathogenic leptomonads of reptiles.

The thermoresistance as determined by the survival time at the action of high and low lethal temperatures has been studied in three Trichomonas species parasitizing the intestine of rodents: Tr. muris from white mice, Trichomonas sp. from Microtus arvalis and Trichomonas sp. from Cricetus auratus. These species appeared to be high resistant to the action of 52—56°, to 4° and to —5°, —10° in supercooling conditions as well. Such a high heat- and coldresistance must be dependent on the body temperature of their hosts. Trichomonads quickly change their thermoresistance in vitro conditions simultaneous with the changes of temperature regime in the same way as it is characteristic of other protozoans.

In white mice exposed to X-irradiation only once reproduction of flagellates, Lamblia muris, Trichomonas muris and Octomitus muris, proceeded more intensively as compared with those in the control. From the places of their usual localization flagellates spread throughout the alimentary canal and were found in considerable quantity even in the stomach. Stomachs of control mice contained no flagellates. Specimens of L. muris were present in tissues of the wall of the small intestine and in one mouse a few representatives of T. muris were found. T. muris and O. muris were found together with bacteria in small abscesses which developed in the liver and spleen. Apparently they penetrated there by a hematogenous way from the intestine.

The paper presents a review of literature and results of the author's studies of general regularities of the development of plague agent population in fleas. The authors believe that the development of the bacterial population in fleas proceeds in four phases: 1) penetration of microbes into the vector's organism; 2) adaptation of bacteria to conditions prevailing in the alimentary tract of fleas; 3) accumulation and preservation of microorganisms in fleas; 4) transmission of the agent to warm-blooded host.

Ultrafine sections of the midgut wall of the body louse were found to contain epithelial cells regarded by the author as resorbtive ones. Their ultrastructure was described. The cells of the tracheolar apparatus are characterized by innercytoplasmatic stripes with plicate walls. Cytoplasm of the epithelium of the malpighian tubes contains rounded bodies with heterogenous content represented, apparently, by the elements of excreta.

The paper describes the larva, protonymph, deitonymph and male of the gamasid mite Haemogamasus kitanoi reared in the laboratory. The distinct species status of Hg. kitanoi and its differences from morphologically close Hg. citelli are established.

The development of Sinergasilus lieni was studied. Three nauplial and five copepodid stages, adult free-living male and female were described. At a temperature of 25 to 27°C the life cycle lasts from 10 to 11 days. The duration of life of parasitic female is about an year, that of male — about two weeks. Under the conditions prevailing in the Krasnodar Territory a female can have up to ten generations; in the Moscow region — one or two generations.

Three new species of two genera are described as follows: Adenicola arabica g. sp. n., Peristedionelia longisetosa g. sp. n., P. mosambika g. sp. n. A new subfamily, Adenicolinae subfam. nov. is erected. A new system of classification of the fam. Plectanocotylidae is suggested and possible ways of the evolution of this monogenean group are considered.

The finding of amylase in solutions containing alive plerocercoids of Ligula intestinalis capable of splitting starch to glucose, a considerable quantity of amylase in the surface layer of the parasite's cuticle and literary data on the presence of microvilli suggest the existence of membrane (contact) digestion in these helminths. The analysis of results obtained indicates that plerocercoids of L. intestinalis have apparently an additional source of feeding on account of the activity of their own ferments which split intensively the food of the host. Membrane digestion of L. intestinalis is likely to be one of numerous forms of adaptation to feeding which arose within the evolution of parasitism.

The paper presents results of experimental studies of the first intermediate hosts of Triaenophorus nodulosus, T. crassus, T. amurensis, T. orientalis from various waters of the USSR (the Rybinsk water reservoir, lakes of Bolshaya Zemlja tundra, the Amur river basin, the Kurilskoye Lake of Kamchatka). In all, 30 species of the suborders Calanoida and Cyclopoida were examined. A role of experimentally infected copepods as the first intermediate hosts of Triaenophorus in nature was evaluated on the basis of the detailed characteristics of their ecology, biology and feeding habits of each species with regard to the intensity of infection in experiments.

The development of cestodes, Retinometra guberiana Czaplinski, 1965 and Parabisaccanthes philactes (Schiller, 1951) in their intermediate hosts, cyclops, was followed by experimental infection. It was established that the development of R. guberiana from oncosphere to invasional stage — larvocysts in Eucyclops serrulatus and Mesocyclops leuckarti — at an average temperature of 23°С lasts 12 to 13 days. The development of P. philactes in Acanthocyclops viridis and Eucyclops serrulatus at an average temperature of 22°C lasts 9 to 10 days.

The disc electrophoresis on polyacrylamide gel demonstrated characteristic differences in the protein spectrum of some representatives of the suborder Paramphistomatata (Szidat, 1936) — Calicophoron calicophorum, Liorchis scotiae, Gastrothylax crumenifer. This method may be used as an additional criterion for the taxonomy of Paramphistomatata.

From 1966 to 1969 35806 specimens of Sagitta elegans were investigated. The specimens were collected from the Chupa Bay of the White Sea. Six species of parasitic worms were found: Brachyphallus crenatus, Derogenes various, Hemiurus levinseni, Scolex pleuronectis, Pseudophyllidea sp. and Contracoecum sp. Annual and seasonal dynamics of the invasion of chaetognaths with different species of parasites was studied. Depending on the region of occurrence of arrow worms vary qualitative and quantitative indices of their invasion with helminths.

Ticks of two species, Ixodes persulcatus and I. pavlovskyi, were found to occur simultaneously in tick-borne ecephalitis nidi of the Kemerovo district. The number of the latter is, as a rule lower, than that of the former but in some places I. pavlovskyi is more abundant than I. persulcatus.

A male of the East-African ixodid tick, Amblyomma gemma Dönitz, 1909, was found on cattle in the Crimea.

Summary is absent.