The penetration of the juveniles through the intestinal tissue caused breakdown of the carbohydrate complexes present in the area and in general the infected intestinal tissue had low carbohydrate content as compared to the control as revealed by several staining procedures. Results of the tests for lipids and proteins were not conclusive. The cytoplasmic RNA of the infected intestine and skin became more pyroninophilic and could account for an increase of RNA content in the infected tissue.

There was an increase of the alkaline phosphatase activity and a decrease in the fibrin content in the infected intestine. Tests for pigments and amyloid and hyaluronidase extraction procedures were inconclusive.

1. B. glabrata exposed to the sublethal concentrations (0·04 ppm, 0·03 ppm and 0·02 ppm) of TPLA died from the effects of the molluscicide over a period of time. Most of the deaths occurred between the 10th and 35th days after treatment, showing that although TPLA is slow acting, its effect is not continuous but restricted to a limited period of time.

2. 0·01 ppm of TPLA was chosen as a sublethal concentration to study the effect of the molluscicide on the development of S. mansoni in B. glabrata.

3. 240 B. glabrata were infected with S. mansoni, and 40 of these were treated with 0·01 ppm of TPLA 4 days before infection. The remaining 200 were divided into 5 groups of 40 each, one group being maintained as a control and the other four treated 2, 10,15 and 20 days postinfection respectively. Other suitable controls for comparison were also maintained.

4. The infection rate in all groups was high, and comparison with the control showed that there was no significant difference in infection rate between the treated groups and the control group at the 5% level. However, the infection rate in the preinfection treated group was lower than in the control group and significant at the 10% level.

A linear relationship was found to exist between (1) the reduced weight and length, (2) the number of contained metacercariae and length, (3) the number of metacercariae and reduced weight, (4) the log. oxygen uptake and the log. reduced weight and therefore, (5) between the log. metabolic rate and the log. reduced weight, in the daughter sporocysts of, Microphallus Pygmaeus.

The life cycle of Gastrodiscoidcs hominis has been described using Helicorbis coenosus as the experimental intermediate host and the pig as the definitive host.

The morphology of the miracidium, redia and metacercaria has been described. Data have been furnished on the infection and longevity, of and production of cercariae by the snail host, and the growth and development of the adult-fluke in the definitive host.

Fourteen species of Monogenea (Dactylogyridae) are reported from fish from the Eilat and Suez gulf littoral. The parasites were collected from fish of 12 species (10 families) and include 9 species of the genus Halioirema (Johnston and Tiegs, 1922) (including four new species), two species of Ancyrocephalus Creplin, 1839 and one species of each of the genera: Atherinicus Bychowski and Nagibina, 1969, Diversohamulus Bychowski and Nagibina, 1969 and Placodiscus n.gen.

A new species Renicola glacialis sp. nov., belonging to the trematode genus Renicola, is described.

The species is distinguished from most other renicolids by its relatively large size. Two other species within this size range have been recorded; while it is easy to separate R. glacialis from one of these species (R. goliath Wright, 1957) the poor description of the other (R. secunda Skrjabin, 1924) renders a detailed comparison meaningless. However, the differences in host and geographic location between this and R. glacialis are considered sufficiently great to justify the erection of a new species.

The pathology of R. glacialis is discussed; recently established worms elicit only a slight host tissue response, but older infections are invested by a thick connective tissue sheath. The latter shows maximum development around dead worms and is accompanied by pronounced eosinophilia.

Attention has been drawn to the use of the excretory vesicle as a diagnostic character. Four distinctly different forms have been described, and it is suggested that this character, together with certain other morphological features, would provide a useful key for the identification of renicolids once such information is available.

During the spring, summer and autumn of 1967, 1968 and 1969, 109 rabbits were collected from two localities in Northumberland. Post mortem worm counts indicated that six species of helminths were present, Trichostrongylus retortaeformis, Passalurus ambiguus, Strongyloides papillosus, Nematodirus battus, N. filicollis and Cittotaenia denticulata.

T. retortaeformis was recovered from both localities, an overall infection rate of 88% being recorded.

P. ambiguus and C. denticulata were found at only one of the localities which would indicate that these species have a locally discontinuous distribution and an explanation for this has been discussed.

Both Nematodirus battus and N. filicollis which are normally sheep parasites were recorded for the first time from wild rabbits. The numbers of rabbits infected and size of infection were small and in consequence the rabbit can not be considered an important reservoir for these species.

Adult Dirofilaria roemeri were transplanted subcutaneously into two grey kangaroos and intraperitoneally into seven laboratory rats in an investigation of amicrofilaraemia, and for experimental transmission studies. Low level blood microfilaraemias of only short duration were produced in all but one rat, supporting the hypothesis that the grey kangaroo is an abnormal host of this parasite. Cortisone was instrumental in the success of D. roemeri in rats. Peritoneal lavage of rats harbouring transplanted D. roemeri proved an excellent source of microfilariae. Injection of large numbers of microfilariae into the saphenous veins of rats harbouring transplanted worms failed to alter the number of circulating microfilariae. D. roemeri failed to develop in Aedes aegypti, fed on rats harbouring transplanted worms and exhibiting blood microfilaraemia. One kangaroo, to which worms had been transplanted, was exposed to the bites of Dasybasis hebes (Diptera, Tabanidae) in the study area and acquired a natural infection of D. roemeri.

The catchment area of the Volta River covers an area of 153,000 sq. miles of which approximately 64,000 sq. miles is located in Ghana. This forms about 70 per cent of the total area of the country. Most of the catchment area in Ghana consists of savanna; including the Guinea savanna of the Northern region, the derived savanna of Northern Ashanti adjacent to it on the south, and the coastal savanna which is separated from the interior savanna by a broad belt of tropical forest. With the exception of some of the headwaters of the Afram the tropical forest is drained by smaller rivers including the Tano, Ankobra and the Pra which are not part of the Volta Basin. Most of the Volta catchment area lies in an area with a well defined wet season occurring between June and September.

In May 1964, the huge dam across the Volta River at Akosombo was completed and the dendritic Volta Lake began to form. It reached its full size after the rainy season of 1968 when it covered an area of approximately 3,275 sq. miles.

A comparison is made of the variations in the mean size (length), reduced weight, oxygen uptake, metabolic rate and the number of contained fully formed metacercariae undergoing autolysis, in mature daughter sporocysts of Microphallus pygmaeus, in sea water, artificial sea water and in a chemically defined nutrient medium (modified medium 199). The work indicates that the sporocysts begin to degenerate almost immediately in the non-nutrient media but have a higher metabolic activity and remain healthy for up to 36 days in the nutrient medium.