Biochemical and histochemical techniques were employed to study tissue distribution, and concentrations of carbohydrate reserves and phosphatase activity in uninfected Mytilus edulis and specimens parasitized by Proctoeces maculatus. Glycogen was stored in the mantle, hepatopancreas, labial palps and mesosomal Leydig cells of the mussel, and in the body parenchyma of post-miracidial stages of the trematode. The glycogen content of the mantle and hepatopancreas increased steadily from January to a maximum level in June and then declined sharply to a minimum level in December. No differences were observed in the annual glycogen cycle of infected and uninfected mussels. Starvation of mussels at a temperature conducive to high metabolic activity of the worms resulted in a rapid decline in the glycogen content of infected mussels by the first week of starvation. A stable glycogen concentration was maintained for 4 weeks by starved uninfected mussels. The distribution of acid phosphatase activity in the tissues of M. edulis and P. maculatus was greater than that of alkaline phosphatase activity, but increased alkaline phosphatase activity was observed in the haemolymph of mussels infected with adult P. maculatus.

The tapeworm Spirometra theileri (Baer, 1925) n. comb., obtained as pleroccrcoids from a wart hog in Tanzania, has been maintained in the laboratory; adults in dogs, and larval stages in Cyclops and then rodents. The species differs physiologically and biologically from those described from other parts of the world in the cyclical production of eggs in dogs, inability of the procercoids to infect amphibia or reptiles, and the lack of any parasite-induced weight gain in mice, rats or hamsters.

A high incidence of lungworm infection occurs in young village pigs, 5 and 11 months old. The mean count was 215 and 315 adult lungwqrms for eleven 5 month and ten 11 month village pigs respectively. All infections were mixed infections comprising M. pudendodectis (69 %), M. apri (18 %) and M. salmi (13 %). No seasonal variation was observed in the rate of infection. A partial immunity to Iungworms is evident in the 11 month old pigs.

In a survey of large intestine material from sheep in North East England, Trichuris ovis and T. skrjabini were recovered. This is the first record of T. skrjabini in Western Europe. The two species can be separated on the length, shape and degree of eversion of the spicule in the male, and on the type of vulval expansion, nature of the vagina and straight portion of the ovary in the female. The relative dominance of T. ovis compared with T. skrjabini in Britain may be attributable to the faster rate of development of the pasture stages of the former species.

Breinlia mackerrasae n.sp. is described from the short-nosed bandicoot Isoodon macrourus. It bears most similarity to B. dentifera, but differs in having larger spicules and in the arrangement of the anal papillae. Female worms from a ‘mumut’ (Peramelidae) are described, but as no males are available, their taxonomic status remains uncertain. These are the first records of Breinlia from peramelid marsupials.

Experiments were constructed to assess the ellects or changes in the diet of Periplaneta americana on Thelastoma attenuatum. Synthetic diets depressed parasitaemia although apparently adequate for the host. However, adult worms were supported best by high carbohydrate levels although protein was necessary for the final moult. Little effect was observed on the distribution of worms within the htndgut although excess roughage appeared to result in a slight backward migration. Egg output per worm remained fairly constant but rose slightly under conditions of extreme stress. Dietary changes affected the size of adult female worms differentially but had little apparent effect on food reserves. Possible reasons for the changes are discussed

Eight species of Monogenea (Dactylogyridae) are reported from the gills of freshwater fishes from Colombia as follows: Anacanthonis colombiamis sp. n. from Salminus affinis Steindachner and Tilapia mossambica (Peters); A. cuticulovaginus sp. n. from S. affinis; Cichlidogyrus sclerosus Paperna and Thurston, 1969, and C. tilapiae Paperna, 1960, both from T. mossambica; Urocleidoides costaricensis (Price and Bussing, 1967) Kritsky and Leiby, 1972, U. hcteroancistrium (Price and Bussing, 1968) Kritsky and Leiby, 1972, and U. strombicirrus (Price and Bussing, 1967) comb. n. (all) from Astyanax fasciatus (Cuvier); and U. anops sp. n. from Characidium caucanum Eigenmann. C. sclerosus and C. tilapiae are recorded for the first time from the western hemisphere.

Allocreadium sudanensis sp. nov. is described from a cyprinid fish (Barbus bynni) from the White Nile in the Sudan. The new species is compared with other related species of Allocreadium.

A key for identification of five African species of the genus Allocreadium is given.

The present material was collected by the senior author in January, 1969 from the intestine of a cyprinid fish, Barbus bynni (Forskal), caught from the White Nile at Rabag near Kosti (about 200 miles to the south of Khartoum) in the Sudan. Eighteen trematodes, collected from a single infected fish, were fixed in hot 70% alcohol. Examination of these specimens in whole mounts stained in aceto-alum carmine and in sectioned material revealed that they belong to a hitherto unknown species of trematodes belonging to the genus Allocreadium, Looss (1900) which is described here as Allocreadium sudanensis sp.

A comparative study was made of the occurrence of the metacercariae of Diplostomum spathaceum, Tylodelphys clavata and T. podicipina in the eyes of brown and rainbow trout, perch, ruffe, roach, ten-spined stickleback, eel and stone-loach, from Hanningfield Reservoir, Essex between January 1968 and March 1969. D. spathaceum was found in all fish species and T. clavata in all except eel and stone-loach. The degree of infection varied considerably between different host species. T. podicipina occurred mainly in young perch but was also found in rainbow trout and ruffe. D. spathaceum normally occurring in the lens was also found in considerable numbers in the humor of the eye in brown and rainbow trout, perch and ruffe. Infection with D. spathaceum and T. clavata increased with length and age of the host although in some host species there was a reduction in the largest fish examined. Newly introduced rainbow trout became infected with D. spathaceum and T. clavata during their first summer in the reservoir.

Metacercariae of two species of trematode (Clinostomum tilapiae, Postodiplostomum nanum) excysted in the stomach of birds, while those of three species (Parorchis acanthus, Posthodiplostomum sp., Postliodiplostomoides leonensis) excysted in the duodenum. Differences were related to the structure of the cyst wall. All could excyst in birds which were not the definitive host and the speed of excystment depended on the speed of movement of food in the gut. All, except P. acanthus, also excysted in the body cavity of the mouse.

There have been few previous reports on the site of excystment of metacercarial cysts in vivo and most indicate that the duodenum is the site for most species studied, e.g. Clonorchis sinensis (Faust and Khaw, 1927), Parorchis avitus (Stunkard and Cable, 1932), Cryptocotyle lingua (Smyth, 1962) and Fasciola hepatica (Smyth, 1966). In their study of the migratory route of Paragonimus westermani in rats, cats and guinea-pigs Yokogawa et al. (1962) found that excystment occurred in the small intestine where the pH range was 5.0–6.0. Also, although the site of excystment has been established for some species, very little quantitative work has been reported about the percentage excystment in vivo and results of work on these lines is reported in this paper.