The suitability of sheep and cattle as hosts for Fasciola hepatica was compared after infection with metacercariae of ovine or bovine origin. It was found that, irrespective of the host of origin, the prepatent periods and the infectivity in both hosts were similar. The flukes in the sheep grew faster, more uniformly and to a greater size, but the individual parasites in the cattle produced approximately twice as many eggs per day as those in the sheep.

Oxysomatiinae: Sexual dimorphism not marked; mouth with three lips; body delicate; pharynx short and muscular; females with ovaries much reduced, uteri divergent, amphidelph, contain a reduced number of eggs arranged in moniliform manner and towards the centre eggs with well developed larvae or even free larvae may be present; vulva behind middle of body; males with subequal or equal spicules of moderate size; accessory piece present. Parasites of amphibians and reptiles. Type species: R. simples (Travassos, 1925) Travassos, 1927.

In August 1962 Dr. C. Amirthalingham brought to me a dead fish, Polypterus senegalus, on which there were a few worms moving. These were found to be monogenetic trematodes of the gyrodactylid type and were later identified as Macrogyrodactylus polypteri Malmberg, 1956.

On examining a tank where a few Polypterus senegalus—from Jebel Awlia on the White Nile near Khartoum—were kept, it was found to be heavily infested with these worms and each fish was covered with a thick greyish-white fluff on its skin. The trematodes could be seen by the naked eye and were found practically on the whole surface of the fishes.

Some 250 substances were assessed for larvicidal activity against the free-living stages of Haemonchus contortus. Most of them were either plant products or chemical compounds found in plants.

Results indicate that promising chemical types worth further investigation are ketones of low molecular weight, alkyl di– and trisulphides, and organic isothiocyanates. Compounds whose molecular structures include the allyl group (e.g. anethole) and the methylenedioxy ring system are potentially active, safrole being particularly effective. Alkaloids as a group were not very effective, but eserine (physostigmine) was outstandingly active, and nicotine sulphate and arecoline hydrobromide showed pronounced activity. Other substances worthy of mention were phenyl mercuric phthalate, galegine sulphate, 8-hydroxy quinoline, methyl salicylate, 10-allyl phenothiazine, guaiacol, thymol, l-limonene and sabinol.

Most of the plant products tested were essential oils: these generally were active, the lowest activity being noted in those oils rich in sesquiterpenes. Activity in the essential oils could be correlated with that of the known compounds.

The study of larval trematode parasites of freshwater molluscs is a field which has been much neglected in Great Britain. Renewed interest has appeared in recent years and this, together with the scattered nature of the literature, has prompted the construction of a key which will aid in the identification of cercarial stages emerging from freshwater molluscs.

In many cases it will be noted that the author and date associated with the species may not be that of the original author but will represent the most recent and complete description of the form. A few of, the early descriptions do not contain sufficient detail to allow very precise demarcation from closely related animals but an attempt has been made to separate them in the present text. As far as possible, easily distinguishable morphological features have been employed, but in some cases reference to the excretory formula and floating position in the water is necessary.

A survey of nematodes from the lower digestive tract of 356 adult domestic fowls indicated that Capillaria obsignata and Ascaridia were more common than was formerly supposed. The incidence of C. candinflata has decreased, whilst that of C. anatis, Heterakis and T. tenuis remains unchanged. These changes may be correlated with the introduction of intensive methods of poultry husbandry.

The distribution of glycogen in the adult common liver fluke, Fasciola hepatica, was studied by the periodic acid-Schiff reaction. As well as in the yolk cells, the peripheral muscle layers and to a lesser extent the parenchyma, glycogen was detected in fine tonofibrils in the tegument.

The glycogen of the peripheral muscle layers and of the tonofibrils of the tegument is drastically depleted if the flukes are kept for a few hours in Hédon-Fleig with insulin added, as compared to controls without insulin.

The effect of insulin raises the question whether this protein enters the tissues through the surface of the tegument, or conceivably but less likely, through the gut. Furthermore, the mechanism of its action in the parasite's tissues requires investigation

A male specimen of Dirofilaria (Nochliella) repens has been recovered from the skin of the right upper arm of a patient from Colombo, Ceylon who manifested signs and symptoms of bancroftian filariasis and had microfilariae in his peripheral blood. This is the second case of Dirofilaria infection reported from man in Ceylon.

Mesocoelium monodi Dollfus, 1929 is reported from Rana (Ptychadena) mascareniensis and Agama agama agama in the Cameroons.

Mesocoelium pesteri sp. nov. is described from a hornless chamelon and compared with related species.

Mesocoelium cameroonensis sp. nov. is described from Rana (Ptychadena) oxyrhynchus and compared with related species.

Guineapigs infected with a lethal dose of Ascaris eggs died between the fifth and tenth day of infection. The M.L.D. was found to be 20,000 eggs. The clinical symptoms and the macroscopic lesions in the liver and lung are described. Infected guineapigs developed an active acquired immunity and repeated infection conferred a high degree of resistance on animals which were subsequently reinfected. Resistance was manifested by the survival of the host following a lethal dose of eggs, and by an inhibition of larval migration. (Less haemorrhage was found in the lung, and fewer larvae were recovered from the lungs and tracheae, after reinfection than following one infection).

The M.I.D. against a reinfective lethal dose 18 days after infection was 500 eggs. The smallest immunizing dose required to give resistance to a challenge 51 days later was 10,000 eggs. This suggests that the resistance manifested at three weeks is greater than that shown after seven weeks, i.e. there is a waning of the immunity.

Guineapigs infected by mouth with eggs of A. suum developed an acquired resistance to reinfection 27, 35 and 51 days later. Resistance of the host was manifested by: survival following a lethal dose of eggs; an inhibition of larval migration; a retardation of larval growth; and the ability to maintain or gain weight.

By means of the conglutinating complement absorption test, using a saline extract of worm as antigen, antibodies were detected in the serum of resistant guineapigs seven days after the second reinfection. Antibodies were not detected in the serum of nonresistant guineapigs seven days after one infection. There was some evidence to indicate that the conglutinating antibody titre of the serum is a measure of the host's ability to resist infection.

Antibodies were demonstrated in the sera of rabbits experimentally infected by mouth with the eggs of A. suum.

An alcoholic extract of freeze-dried ovaries, oviducts and uteri of adult female Ascaris worms was used as an antigen in the complement fixation test, and a polysaccharide fraction and a saline extract of whole worms were used as antigens in the conglutinating complement absorption test.

In all rabbits the pattern and nature of the antibody response was similar using the three different antigens. When the saline extract antigen was used in the C.C.A.T., antibodies were detected earlier, and titres were recorded higher, than when other systems were used. The degree of response was proportional to the size of the infective dose. Circulating antibody first appeared between the third and eighth days of infection. The highest concentration of serum antibody was reached between the eighth and twenty-first days, and in those animals which received large doses the maximum response occurred about the third week. By repeated twice-weekly infection antibody was demonstrated in the serum for 114 days.

A survey for parasites has been undertaken in 20 mountain gorillas (Gorilla gorilla beringei) from the Eastern Congo Kivu province.

Six full-grown (two males and four females), three adolescents (one male and two females), and eleven young gorillas were examined, some of them during several consecutive months. Nine autopsies were performed.

No protozoa were discovered in the blood. Plasmodium parasites which are common in gorillas and chimpanzees from West Africa were never found in the Eastern Congo primates, including ten other gorillas examined previously and some fifty chimpanzees. Severe diarrhoea with a balantidiasis picture developed in two young gorillas. Autopsy revealed however an intensive infection with Oesophagostomum stephanostomum and resulting fatty degeneration of the liver. Oligotrichida belonging to the genus Troglodytella were commonly found in the intestinal tract. Oesophagostomum stephanostomum eggs were consistently present in the stools of the gorillas and autoinfection caused the death of several young gorillas 4 to 6 weeks after their capture.

Recent collection of lung fluke material from hydrophiid sea snakes permits a reevaluation of the suitability of criteria separating the monotypic genera Pulmovermis Coil and Kuntz, 1960 and Hydrophitrema Sandars, 1960. Consideration is also given of the new subfamily Pulmoverminae, erected by Sandars (1961) to include these genera within the digenetic family Hemiuridae. Typographical errors in the original description of H. gigantica Sandars, 1960 have been corrected, reducing the gross or external measurements of that species by ten times. Validity of characters such as flexure of the body, location of testes and ovary with respect to body length, length of seminal vesicle compared to body length, and anterior extension of the seminal vesicle with respect to acetabulum have been rejected. Retained are general body shape, relative position of acetabulum and development of peduncle, degree of coiling of seminal vesicle, and tandem or oblique arrangement of testes. Characters newly employed include body length-to-width ratio and presence of a cuticular fold in Hydrophitrema enclosing both suckers. Retention of the present genera based on these revised characterizations is recommended. Subfamily criteria (form, structure, and size of seminal vesicle, shape of vitellaria) are similar to those employed among the other nineteen subfamilies of this large and possibly heterogeneous group. In addition, these flukes are unique within the family on ecological and physiological grounds, in that they parasitize the lungs of sea snakes rather than the stomach of marine fishes, the usual site and host for members of this family.

This paper concerns the relationships between miracidia of Schistosoma haematobium from Aden and various species of the Bulinus complex. It includes evidence on penetration and further development within the snail as revealed in serial sections.

During the course of studies on the mechanism of penetration by miracidia of Schistosoma mansoni into their intermediate hosts it was found that commensal annelids of the genus Chaetogaster frequently preyed upon the attaching larvae. Wagin (1931) found cercariae in the gut of Chaetogaster and Wesenberg-lund (1934) confirmed Wagin's finding. Wallace (1941) reported that these worms serve as second intermediate hosts for some trematodes and when cercariae of Trigonodistomum mutabile were ingested by Chaetogaster limnaei they penetrated the gut wall and encysted in the body cavity. When the worms with their metacercariae were fed to fishes the adult trematodes were later recovered. Ruiz (1951) working on Schistosoma mansoni noted that the Chaetogaster ingested the cercariae liberated from the snail. Khalil (1961) further noted when observing experimental infection of Lymnaea natalensis with miracidia of Fasciola gigantica that these worms ingested the miracidia, and he found that the majority of these worms had a variable number of miracidia in their gut.

A total of 431 rats, collected twice monthly during one year from the same locality (a slum-commercial area of approximately 1 km2 in the southern part of Tel-Aviv), were examined for the presence of S. ratti and S. venezuelensis. Of the 431 rats examined, 154 (35.7%) were found infected as follows: 48 with S. ratti, 37 with S. venezuelensis and 69 with both species. A seasonal fall in infection, from a high incidence of 78·9% in February to a low incidence of 4·5% in September was noted, which roughly corresponded to the monthly rainfall. The persistence of infestation throughout the rainless summer months is probably due to seepage from surface structures (warehouse depots, dripping outdoor faucets, faulty plumbing, etc.). The monthly incidence of both species of parasite according to age and sex of the host is discussed.

Methods for isolating the various stages of parasite life-cycles in large amounts and in a clean condition for biochemical and immunological studies are urgently needed. Among the parasitic nematodes the methods so far developed mainly concern the adult worm, though the eggs of some of the Ascaroidea are notable exceptions. This paper describes adaptations of one of the traditional methods of culturing Nippostrongylus infective larvae which satisfy the needs of biochemical and immunological studies.