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The role of 11 species of the genus Ornithodorus in the transfer of various species of spirochaetes was studied (tab. 1). 99 tests were carried out, 2623 ticks were used. It has been established that each species of the vector tick can preserve for a long time and systematically transmit only one species of spirochaetes. The transmission occurs practically in all cases (tab. 2). An exchange of spirochaetes between allied species is possible. In rare cases the ticks can transmit spirochaetes, which are normally characteristic of taxonomically distant species. Out of 83 tests on the infestation of ticks with non-typical spirochaetes, positive results were obtained in 11 cases. The transmission of "strange" spirochaetes was of short duration and unstable in its character. The lick O. canestrinii preserved spirochaetes about 18 months and never transmitted them during feeding.

The development of larvae and nymphs of Ixodes persulcatus P. Sch. (excluding diapause) in relation to season of their feeding, temperature of forest litter during the development of ticks and ecology of individual geographical populations were studied. Statistically valid differences in the duration of the development of larvae and nymphs were established even during their feeding in different decades of the same month. These differences depend on the seasonal changes in the warming of forest litter (coefficient of correlation — 0.9). There were found deviations from regular relationships between the duration of the development of larvae and temperature: at the same average daily temperature the rate of the development of ticks in years with cold summers and strong daily and seasonal fluctuations in temperature was higher than was that in years with warm even temperature. The same were differences between the rates of the development of larvae in areas with different degrees of conl inentality of the climate. Hereditary differences in ecological requirement were found in individuals from south Primorje (Far East), which were compared with the Moscow and Siberian populations of I. persulcatus.

The distribution of Citellus major Pall. and C. suslicus Güld. over the Volga-Kama territory and their infestation with lice confirms the general opinion that at the boundaries of their areas host species are small in number and poorly infested with parasites. On the other hand species extending their areas intensively (C. pygmaeus Pall.) may be very abundant at the boundaries of their areas and highly infested with specific ectoparasites, lice in particular, which are closely connected with the host. During the active period of life the infestation with lice in adult males does not undergo great changes. In females infestation the sharply decreases during lactation, when the greater part of the parasites leave adults for sucklings, and greatly increases after the settling of young animals in their own burrows.

The paper contains new data on the fauna, ecology and biological peculiarities of gad-flies from Chuiskay valley and Kirghiz mountains. Observations have been done in the summer 1966. 15 species of 5 genera were found, viz., Chrysops, Hybomitra, Atylotus, Tabanus, Haematopota. These gad-flies are most rich in species in the semidesert zone, where H. acuminata, H. peculiaris and Haem. pallens dominate. In higher mountain zones their fauna is much poorer in species but gad-flies are very abundant. H. hunnorum, H. turkestana and H. montana reinigiana are recorded as dominant in this zone.

The time of uninterrupted stay of fleas of great gerbil Xenopsylla skrjabini loff on their host (the time of single stay) is relatively constant for a definite season. It is a specific adaptation to the mode of life of the host and changes within a year due to changes in the feeding activity and reproduction of fleas. In spring X. skrjabini stays on the host about 18—24 hours, in summer — 12—18 hours, in autumn — about 4 days . Fleas of great gerbil, Coptopsylla lamellifer Wagn. stay on the host about one hour. The formation of the plague block in infected X. skrjabini depends on the duration of their stay on the host during feeding. During all seasons the longer the stay of fleas on the host, the quicker the formation of the plague block. This dependence manifests itself especially in spring, in the period of intensive feeding and reproduction of fleas. With a longer feeding period (from 4 to 24 hours) the period of block formation decreases 2 times and the number of infected fleas increases 2.5 times. The leading role in the plague transmission belongs (in case of great gerbil's fleas) to the members of the genus Xenopsylla and depends mainly on their long uninterrupted stay on the host.

The paper deals with some results of light- and electronmicroscopic studies of the cuticle and the subcuticular layer in the procercoid, plerocercoid and immature, mature and degenerative adults of Triaenophorus nodulosus (Pall.). It has been established that in these phases the cuticle is covered with microtrichia of two types, large and small; the cuticle contains vacuoles and is connected with the subcuticular cells by means of cytoplasmic intercellular bridges. Only in the procercoid is the cuticle connected with the subcuticular cells by means of a fully formed channel which is filled with tubes. Microtrichia are present over the whole surface of the cuticle in all parasitic phases. A comparison between the cuticle in Triaenophorus and that in other cestodes was carried out. It is suggested that microtrichia in cestodes are the organs of absorbtion of food, and which appeared as a result of adaptation to a parasitic mode of life due to the absence of the digestive system.

It was suggested to use a generally accepted method of the separation of the faunistic type from the whole faunistic complex for zoogeographical analysis of the fauna of helminths. This method was successfully used for the analysis of the fauna of acanthocephals found in Subarctic birds. A faunistic type of acanthocephals recorded from Subarctic birds (18 species) was distinguished from the whole faunistic complex (60 species). The group is most various in East Siberia, Chukotka, Beringia and Alaska, which, apparently were the centre of the origin and primary migration of a given faunistic type both of Subarctic birds and their acathocephals.

The distribution of DNA and RNA has been studied in nuclei of integumentary tissues of Macracanthorhynchus hirudinaceus (subclass Gigantorhynchinea), Polymorphus magnus, Acanthocephalus ranae and A. lucii (subclass Echinorhynchinea). The hypodermal nuclei in these worms are shown to have different types of distribution of DNA, specific for each species. Macracanthorhynchus hirudinaceus has been found to have a diffuse type of distribution of DNA. It is supposed that the specificity of the distribution of DNA in hypodermal nuclei is to a certain extent a taxonomic character.

Two females of Gongylonema pulchrum were recorded for the first time from porcupines in Karabakhsky ridge (Transcaucasia). The females were found under the oesophageal mucous membrane.

In 1956—1966 a parasitological investigation of 1680 birds, belonging to 139 species of 15 orders was carried out in the Kaliningrad region. 98 species of nematodes were found. Descriptions of new and rare species are given. 1. Capillaria belopolskaiae Jogis, sp. nov. (figs 1—4) — from the intestine of Gallinago gallinago (L.). 2. Thominx similis (Kowalewski, 1903) Jogis (figs 5—7) — from the intestine and the colon of Garrulus glandarius (L.), Turdus philomelos Brehm and Sturnus vulgaris L. 3. Th. totani (Linst., 1875) (figs 8—10) — from the caeca and the colon of Actitis hypoleucos L. Females of this species differ from those of Capillaria breve (Linst., 1877). The unification these two species by Lopez-Neyra (1947) seems to be invalid. 4. Hadjelia sp. (figs 11 —14) — from the proventriculus of Tringa glareola L. 5. Physaloptera saginata Rud., 1819 (?) (figs 15—18) — from the intestine of Caprimulgus europaeus L. 6. Alinema sturni Jogis, gen. et sp. nov. (figs 19—24) — under the cuticle of the gizzard of Sturnus vulgaris L.

The development of Aphelenchoides besseyi Christie was found to begin at 13° C; the range of optimal temperatures suitable for its reproduction is 20 to 30° C. For completion of the life cycle at 21—23° C, a time interval is necessary, during which the sum of the effective temperatures amount to 80° C, on the average. The duration of the life cycle of A. besseyi is 10 and 8 days at 21 and 23° C, respectively.

A case of "endotokia matricida" was recorded in Ditylenchus dipsaci (Kuhn). This phenomen may arise in nematodes due to the age degeneration of females or due to unfavourable environmental conditions.

Studies of nuclei from blood of dogs and cattle were carried out by means of Feulgen's reaction and staining according to Unna. It has been established that pyriform individuals have only one nucleus, which contain a small accumulation of DNA (in the shape of half-moon or crescent). Often one or two feulgenpositive granules are visible in nucleus. Considerations of various authors concerning the presence of two nuclei in Piroplasma or one nucleus and blepharoplast or two "chromatin" accumulations are not true since they are based only on results obtained by staining according to Giemsa-Romanovsky. The so-called additional nucleus, blepharoplast or "chromatin accumulation" do not contain DNA. They involve either a digestive vacuole or accumulation of RNA, glycogen and alkaline phosphatases (Ray a. Sengupta, 1956) which are red stainable according Giemsa-Romanovsky.

Cytological and immunological-fluorescent studies (by the direct method of Coons) were carried out on spreads of the omentum in white mice, which were infected with RH strain of Toxoplasma gondii. The combination of both methods gives a true picture of the occurrence of the parasite in the host and of the local responce of the peritoneum. The intracellular reproduction of toxoplasms in the omentum is confirmed. The formation of terminal colonies of toxoplasms occurs in parallel with their disintegration and the separation of parasites. The reproduction of toxoplasms occurs mainly in omental histocytes and peritoneal mesothelium. The inflammatory reaction of the host to the viruJent strain of T. gondii is not sufficient to withstand the infection.

Summary is absent.

Summary is absent.