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Summary is absent.

Cnidosporidians are regarded as an independent branch which attained the state of multicellularity. A role of polymerisation and oligomerisation of homologous and homodynamic organelles in the evolution of Protozoa and the origin of multicellularity are discussed.

Triaenophorus nodulosus and T. crassus from Europe and Siberia have some distinctions in morphology, in host circle and biology from the inhabitants of the Amur basin, and T. crassus even differs from that ones of the southern reservoirs of the European part of the USSR. These distinctions give all the grounds to consider T. nodulosus and T. crassus from the Amur basin and T. crassus from the southern reservoirs of the USSR as independent species named accordingly T. amurensis sp. n., Т. orientalis sp. n. and T. meridionalis sp. n. Thus, allongside the well-known species T. nodulosus, T. stizostedionis and T. crassus one ought to distinguish 6 species of the genus Triaenophorus.

Three species of cestodes of the genus Globarilepis Bondarenko, 1966 were found in waders from the coast of the White and Baltic Seas. Species of the genus Globarilepis differ from those of the genus Aploparacsis in having their eggs in the uterus enclosed into capsules. The capsules of Globarilepis groved to be secretory in their origin. That is why they are referred to as pseudocapsules and the genus Globarilepis is reduced to the subgenus of the genus Aploparacsis.

In 1967 Bothriocephalus gowkongensis was first found in the delta of the Volga. Bothriocephalus was recorded from three of six fishes investigated, namely white amur, common carp and pike-perch. A further extension of the range of definite hosts may be expected.

In the Astrakhan region Bithynia leachi is confined to temporary water bodies of the Volga-Akhtuba flood-plain, upper zone of the delta and contiguous western regions. The life activity of mollusks depends on spring-summer flood. The leading part in the spread of the invasion belongs to domestic pigs of the Volga-Akhtuba, the infestation of which reaches 40%. Carnivorous animals are unessential in the invasion spread. In the lower delta of the Volga the agent completes its life cycle in definitive hosts. In the Volga-Akhtuba region the infestation of man and animals can be through such fishes as rudd, silver bream and bleak.

In the Altai territory Philometra sanguinea Rudolphi, 1819 was found to be the causative agent of philometrosis in crusian carps. Analysis of the available literature has shown that Ph. carassii Ishii, 1933 and Ph. trilabiata Belouss, 1965 are the synonyms of Ph. sanguinea Rudolphi, 1819. Females of the three species parasitize the fins of crusian carps; their morphological characters and colour of the body are identical (table I). The descriptions of Ph. sanguinea by different authors are analysed. The species is assumed to be a specific parasite of crusian carps, its finding in other species of fishes is evidently erroneous.

The effect of hygromycin В on larvae and young forms of Ascaridia galli in the host was studied. The hygromycin В was proved to inhibit the growth and development of parasites which had already passed the tissue phase.

It was established experimentally that isopods (Iaera albifrons ischiosetosa) can be concerned in the life cycle of the fish parasite Contracaecum aduncum as an intermediate host. Certain moments in the organogenesis of larvae of C. aduncum were detected. Studies of isopods for spontaneous infestation with this parasite also confirmed that they can be involved in the life cycle of C. aduncum.

Morphometric comparison of Ditylenchus dipsaci from strawberry, onion, hyacinth, phlox and red clover and D. destructor from potato has revealed permanent differences between these species. Stem nematodes do not differ actually from each other and from the well-known type D. dipsaci. The species status of stem nematodes from strawberry and phlox is accepted invalid; the independence of Ditylenchus allii (Beijerink, 1883) Kirjanova, 1951 is questioned; the conclusion is drawn that the species name D. trifolii Scarbilovich, 1957 cannot be used for populations of the stem nematode from red clover.

Ixodes pavlovskyi and I. persulcatus were previously reported to be allied but distinct species of the genus Ixodes Latr. inhabiting the forest zone of south-western Altai. The immature phases of these species were shown to live in close contact, i.e. they share the same habitats, parasitize the same species of hosts. Comparative-morphological characteristics of larvae and nymphs of I. pavlovskyi and I. persulcatus are based both on ticks reared in laboratory and those collected from wild vertebrates in south-western Altai. For differential diagnostics of the species such structures were chosen the form and sizes of which do not transgress or give statystically reliable differences. Larvae differ in form and size of hypostome, size of palps and scutum, form of medial spurs of coxae I. Nymphs differ in form and size of gnathosoma, scutum and coxal spurs.

Judging by the decrease in oxygen consumption and reduced body weight of infected fleas, microbes of plague exert a toxic effect on them. In response to the inoculation of the microbes a lysogenous substance is formed in fleas that favours the purification of most of infected specimens from the agent of plague.

The external morphology of III^d instar larvae of fleas is described. 6 genera of the family Pulicidae were examined: Pulex Linn., 1778; Echidnophaga Oll., 1886; Archaeopsylla Dampf, 1908; Ctenocephalides Stiles et Collins, 1930; Xenopsylla Glink., 1907 and Spilopsyllus Bak., 1905. The key is given.

A key is given to IV^th stage larvae of 29 species, which is based on the characters distinguished by Kettle and Lawson (1925) and Glukhova (1968). Characteristics are given to the main groups of species and some species which are not included into any group.

In forest-tundra of the Dudinka region of the Taimir National district Culicoides pulicaris, C. pascipennis and C. okumensis were collected from man and animals in warm summer seasons. In cold years midges were not recorded there. In mountain tundra of this region midges were not recorded at all. In northern plain tundra of the Khatanga region not far from the border with Jakutia only single males and females of C. pulicaris pulicaris were observed early in July, 1967. The flight of midges was from the end of July to the end of August.

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Summary is absent.

Summary is absent.