The anterior end of the miracidium of Fasciola hepatica contains a large flask-shaped apical gland and four unicellular lateral glands, all of which have ducts which pass to the tip of the apical papilla. These glands appear to be involved in penetration of the larva into the snail host. The apical gland secretes as the miracidium proves the epidermis of the host before attachment. It seems likely that its secretion is a chemical which lyses the epidermal cells. The lateral glands are PAS-positive and may contain a neutral mucopolysaccharide. They also secrete as the miracidium probes the snail and a layer of PAS-positive material may be seen at the leading edge of the apical papilla as the larva penetrates into the host. Both the apical gland and the lateral glands may be visible in the sporocyst for several days after penetration.

By means of scanning electron microscopy, aspects of the attachment of Moniliformis dubius (Acanthocephala) to the intestinal wall of the rat are described together with various changes in the structure and form of the mucosa. Attachment of the parasite results in the formation of a distinct pit around the everted proboscis and a crater around the neck. Contact between the anterior region of the trunk of the worm and the intestine of the host appears to lead to villous fusion so that characteristic grooves are formed in the mucosal tissue. Evidence was also obtained to suggest that host goblet cells may become exhausted during the course of an infection with Moniliformis.

Metacercariae identified as those of the heterophyid trematode, Galactosomum ussuriense were collected from 3 species of brackish water fishes from Bheemunipatnam. The organization of the the larva is described in detail. This is the first record of the metacercaria of this species although the adult has not so far been recorded from India.

Congenially athymic nude mice (BALB/c-nu/nu) and BALB/c-nu/+ were infected with 500 embryonated Toxocara canis eggs. Six weeks later they were reinfected with the same number of eggs. The liver and other organs were examined for numbers of 2nd-stage larvae at 2,4, and 6 weeks after reinfection. Far more larvae were trapped in the liver after reinfection than after the primary infection but fewer were found in the livers of BALB/c-nu/nu than in BALB/c-nu/+ mice.

Electron microscopic observations were made on unhatched eggs of Taenia crassiceps in utero. The outermost envelope consists of a thin, relatively smooth capsule over a highly convoluted outer envelope which contains a highly granulated cytoplasm and numerous mitochrondria. The inner envelope, consisting of a thick embryophore and the cytoplasmic component of the embryophore cell, resembles that found in most other taeniids. Three epithelial layers separate the oncosphere from the embryophore. While these layers are narrow and difficult to distinguish, the ‘oncospheral membrane’ is distinct, darkly stained and relatively thick. The oncospheral hook lies within the oncoblast with its blade portion held by cytoplasmic folds within a modified ‘sheath’ in the ‘basal epithelial layer’. Round, dense bodies are concentrated at the epithelial membranes around the ‘sheaths’. Hook muscles insert on the basal lamina at the ‘collar’ region of the hooks. Penetration gland cells are packed with numerous dense disc-shaped secretory bodies.

Female Gallus gallus L. are more susceptible to Heterakis pusilla than are male hosts. The worm burden decreased with increase in size and weight of domestic fowls. The frequency distribution of H. pusilla in the two sexes, and by host's size and weight classes was log-normal.

The antigenic properties of adult male and female of Dipetalonema viteae were studied by immunocytochemistry. Using antisera of the rodents Meriones unguiculatus and Mastomys natalensis infected with D. viteae, the binding of antibodies to sections of filariae embedded in Epon was assayed by the peroxidase-antiperoxidase (PAP) technique and by electron microscopy. The optimal staining intensity was obtained with an antiserum dilution of 1:5000. Control sera were obtained from sex and age matched uninfected animals.

Female D. viteae showed maximal antigen-antibody reactions within the uterus: in the inner uterus wall, in the “nutrient channels” between the maturing eggs and the differentiating microfilariae, on the eggshells, in the cuticula of microfilariae and in the spermatheca on the cell membrane of the mature spermatozoa. Male filariae showed binding of antibodies in the vesicula seminalis: in the nucleus and the nuclear membrane of primary spermatocytes and on maturing spermatids. Less pronounced antigen-antibody reactions in the cuticula, muscle and intestine were observed in both sexes.

The PAP-technique offers significant improvements in comparison with other techniques, e.g., immunofluorescence, used to detect antigens on filariae: the PAP-technique has an increased sensitivity with a concomitant reduction in nonspecific background and can be used for both light and electron microscopy; moreover, PAP-treated tissues can be stored indefinitely at room temperature.

Thometrema magnifica from Hypostomus commersoni and Loricariichthys anus (new host) is redescribed with additional morphological data and original figures, measurements and figures of Szidat's paratypes. Gibson & Bray's hypothesis that T. portoalegrensis is its synonym is confirmed.

The oocapt of Paramphistomum cervi has a narrow constriction followed by a wide lumen with a thickened wall and is surrounded by several unicellular flask-shaped gland cells opening into the lumen. The oocapt gland cells are filled with granules, the size and number of which vary in the body cells and its duct. Histochemical studies have shown that the oocapt gland cells secrete mainly mucoproteins but a few lipoprotein and phospholipid granules have also been observed. The passage of the oocyte through the lumen of the oocapt, appears to stimulate the oocapt gland cells to release their secretion which seems to be involved in transport of the oocyte through the oviduct.

Rats acquired a degree of protective immunity to reinfection with Angiostrongylus cantonensis after a single infection with 50 infective larvae. Infected rats resisted the establishment of most challenging larvae and protective immunity increased with subsequent reinfections. Part of the primary infection was lost after a superimposed second and also following a superimposed third infection, but the total size of the concurrent adult worm populations remained the same as that from a primary infection. Worms surviving from the primary infection showed enhanced growth after each reinfection but their fecundity was impaired.

Over 26000 specimens representing five euphausiid species collected, mostly in 1969, in the North-East Atlantic and northern North Sea were examined for parasites. Hysterothylacium sp. larvae were rare, occurring in only two euphausiid samples from inshore localities; the 9 larvae found (3.8 to 12.3 mm long) are described and illustrated. Infection with larval Anisakis simplex was virtually restricted to Thysanoessa spp. and appeared to be discontinuous. Infection was absent to the west of Scotland, and rare to the north of Scotland and at the Faroes. Larval A. simplex was not uncommon in offshore regions of the northern North Sea at depths between 100 and 200 m; the prevalence rate there for individual euphausiid species in individual samples was mostly 0 to 40% but an exceptionally high rate of 78.0% was recorded. Larvae in euphausiids do not become encapsulated but appear to remain active. Experimental observations on the sedimentation rate of A. simplex eggs and hatched larvae in sea water at 10°C are discussed in relation to embryonation and hatching at different temperatures, and depth of the sea. New host records are claimed for larval A. simplex in Nyctiplutnes couchii, and for larval Hysterothylacium sp. in Thysanoessa inermis. No individual euphausiid harboured more than one parasite, either larval nematode or ellobiopsid (see also SMITH, 1981). Morphological and morphometric observations on larval A. simplex from euphausiids are reported elsewhere (SMITH, 1983).

Four little-known ascaridoid species occurring in crocodilians are discussed. Typhlophorus lamellaris Linstow, 1906 and Hartwichia rousseloti Chabaud& Bain, 1966 are considered to be closely related to Heterocheilus tunicatus Diesing, 1839; Porrocaecum assymmetricum Ortlepp, 1932 is transferred to Trispiculascaris together with T. trispiculascaris Skrjabin, 1916. These three genera are placed in the subfamily Heterocheilinae sensu Sprent (1980) on account of the structure of the oesophago-intestinal junction, the labial pulp and, where known, the male tail. A key to eight genera of Heterocheilinae in crocodilians is provided.