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The anatomy of the nervous system of Udonella caligorum is described. The nervous system is represented by orthogon, three pairs of longitudinal stems, transverse commissures and nerve plexus. Neurons are small in number and have an invariable arrangement. The characters of the nervous system as well as of the other systems suggest the phylogenetic affinity of Udonellida and Temnocephalida.

A comparative description is given of different connective tissue cells and the character of intercellular substance in the parenchyma of two species of cestodes of the order Pseudophyllidea and 4 species of the order Cyclophyllidea. The parenchyma of the cestodes has been shown to be a complex specialized tissue system evolving divergently. The first distinct morphological differences arise at the family level. The direction of the divergent evolution of the parenchyma depends on the development of certain components of intercellular substance, frequencies of individual types of cells and appearance of specific cellular element in it.

Data are given on the larvogenesis of the diplocyst of Aploparaksis furcigera. The invagination process of the metamere is described. The external layer of duplicature (exocyst) of the diplocyst has been shown to be a derivate of a typical cercomere. Due to this the larvogenesis of the diplocyst of A. furcigera is regarded as a cystocercoid larvogevesis changed by the adaptation to parasitism in polymyarian intermediate hosts (Oligochaeta). The origin of protective cenogeneses of diplocyst is a response to mechanical effects of the cutaneous-muscular sac of Oligochaeta upon the developing larvocyst.

Cercariae of Echinostoma sp., Cotylurus cornutus, Cercaria С Szidat, marites of which parasitize homeothermic hosts (birds), were found to have a high heat resistance at the effect of lethal temperature. There were established specific differences in the temperature level and its stability during a long period at a relatively constant environmental temperature. The heat resistance of cercariae of the same species does not change during their parasitism in different species of mollusks, hosts (e. g. С. С Szidat). Thermoresistance of mature cercariae of С. С Szidat and Cotylurus cornutus having entered the water is in agreement with the environmental temperature and changes with a temperature regime of the environment. Even an acclimation within 3 hours at 29° results in a rise of the heat resistance of cercariae. Their stay at 4° within 3 hours decreases two times the heat resistance.

The nematode fauna of winter wheat and wild cereals in the foothill zone of Dagestan is richer than that in the lowland zone. From 117 species of nematodes recorded from the rhizosphere and organs of examined plants 105 species are reported from foothills and only 78 species from the lowland zone. In the foothill zone the average number of nematodes in 10g of root soil and organs of wheat amounts to 619 specimens, in wild cereals — to 347 specimens, in lowland zone — to 310 and 236 specimens respectively. This difference is caused by soil-climatic conditions.

The polyacrylamide-gel electrophoresis was used to separate the negative charged proteins from adult females of the tick Dermacentor marginatus Sulz. There were separated up to 25 protein bands from haemolymph and up to 19 bands from midgut extracts of the engorged females. The number of protein bands in excreta and eggs was 15 and 18 respectively. Haemoproteins from haemolymph, midgut and eggs were different in their electrophoretic mobility. Active and diapausing ticks showed essential differences in protein spectra and content of haemolymph (the enrichment of them was characteristic of diapausing ticks). The presence or absence of reproductive diapause affects the digestive functions and has no influence on the excretory functions of the midgut.

576 nests of 7 species of rodents were investigated. 9341 specimens of fleas and their larvae belonging to 18 species were collected. The occurrence of fleas in the nests of different hosts in 12 habitats and changes in the inhabitance level of the nests with fleas under the effect of drainage are described.

Specimens (imagos) from the collection of the Zoological Institute of the Academy of Sciences of the USSR were investigated. Within the territory of the USSR this species is represented by four main geographic forms, subspecies, distribution areas of which overlap each other a considerable extent. The subspecies are connected by gradual passages.

In summer of 1973—1974 a comparative counting of the number of sandflies was carried out by two methods in the Turkmenian Soviet Socialist Republic. Sheets of oil paper fastened vertically to two wires at a height of 60 cm above the ground at a distance of 20 cm one from another (barriers) and sheets in the form of "flags" (Dergachova and others, 1973) were used simultaneously. 15860 sandflies (X on one sheet 31.2±3.2 specimens) were collected on 50 barriers consisting of 10 sheets each; and on 500 flags 7640 sandflies (X on one flag 15.3±1.37 specimens) were collected. When sandflies are caught on flags the coefficient of counting equal to 2.1±0.37 should be taken.

Studies were undertaken of the life cycles of three intestinal coccidia: Eimeria arabiana, E. bistratum and E. poljanski, parasites of Meriones vinogradovi. Thenumberof the asexual generations, the period of appearance of the endogenous stages and the first oocysts, localization were determined. The successive phases of the growth and development of schizonts of different generations, macrogametes and microgametocytes were described. The distribution of DNA and RNA in different endogenous stages of three kinds of coccidia were studied by methods of cytochemistry.

Some morphological and cytochemical methods were applied to the study of the life cycle of Trichomonas parasitizing the intestine of various rodents. The comparative study of trophonts morphology showed that the only species of the genus Trichomonas — T. muris inhabits the intestine of mice, rats, field-voles, hamsters and susliks. The life cycle of T. muris includes three morphologically different stages: trophonts, pseudocysts and cysts. The pseudocysts and cysts are the infectious stages of T. muris. All rodents ingest them together with their food. The cysts of T. muris can survive for a long time (6 months and more) in the environment under the conditions of various temperature and humidity.

A little-known species of mosquito, Aedes (O.) rempeli Vockeroth is described. According to its structure and ecology the species belongs to the group A. communis and by the complex of its characters (according to the key for identification of females, Gutsevich, Monchadsky, Stakelberg, 1970) the species corresponds to the diagnosis of A. communis. The females of A. rempeli differ from this species by light bands at the bases of tergites narrow to the middle.

5 species of myxosporidians of the genus Chloromyxum were found in the gall bladder of Chondrostei from the Pathagonian shelf (Argentina coast). 4 species of them are new ones. This indicates that the species Chloromyxum leydigi mentioned for all Chondrostei is a collective species which needs a revision. Caudal filaments and ribs of the valves of spores of myxosporidians are more developed in species parasitic in fishes getting food from water mass and predators and to a lesser extent in species getting food from the bottom.

In the biocoenosis of the lake Tengiz (Central Kazakhstan) Artemia salina (3.3%) and Branchinella spinosa (0.22%) were found to be infected with larvae of cestodes — delipidids Anomolepis averini (Spassky et Yurpalova, 1967). Phalaropus lobatus from this water body was also infected (13.7) with this cestode, the infection intensity being from 1 to 15 strobiles in one bird. Figures and morphological description of cysticercoids and mature cestodes of Anomolepis averini are given.

A gall nematode, Meloidogyne arenaria (Neal, 1889) Chitwood, 1949 was found in the close ground of the settlement of Paratunka, Elizovsky region, Kamchatka. A description and figures of the species are given.

Summary is absent.

Summary is absent.

Summary is absent.

Summary is absent.