Dictyocotyle coeliaca is recorded for the first time from Raja fullonica and R. batis. It is suggested that normally D. coeliaca may be restricted to waters deeper than about 50 fathoms and that this should be considered in attempts to incubate its eggs in the laboratory. No Calicotyle kroyeri were present in female R. radiata which contained eggs in their uteri and a brief account is given of the apparent differential distribution of the species in male and female rays. Up to 64 specimens of C. kroyeri per fish are recorded from the cloacae of R. radiata (previous records refer to an average of about four specimens per host). In a brief discussion of the controversial papers on these two monogeneans reasons are given for retaining the two in separate genera.

I am most grateful to the following for providing excellent facilities for the work. The Director and staff, in particular Dr B. B. Rae and Dr Z. Kabata, Marine Laboratory, Aberdeen; the Director and Staff, Plymouth Marine Laboratory; Professor James Brough, University College, Cardiff; the Director, Commonwealth Bureau of Helminthology; and Mr H. Atkinson of Messrs J. Marr and Son, Fleetwood. Additional specimens were provided by Mr J. Slinn, Marine Biological Station, Port Erin, and by Mr J. W. Smith of this Bureau.

The results are described of a study of the distribution of the antigens in F. hepatica at various stages of development, and in the liver and spleen of experimentally infected rats using globulins labelled with fluorescein isothiocyanate, from rats and sheep infected with F. hepatica.

Possible uses of this technique in aiding the diagnosis of fascioliasis are indicated.

I wish to thank Dr A. W. J. Broome for a supply of the metacercariae of F. hepatica, and Dr J. S. S. Lowe who kindly isolated and labelled the globulins with fluorescein isothiocyanate. Miss Enid Eccleston gave valuable technical assistance.

The cyst wall which encloses the metacercaria of Fasciola hepatica consists of four major layers, one of which is further divisible into three sublayers. These layers are numbered I to IV, the first being the external layer. Layers I and II form the outer cyst which may be separated from the inner cyst formed from layers III and IV.

Layer I, the thick incomplete external layer, covers the metacercaria dorsally and laterally. It is composed of tanned protein.

Layer II is a thin fibrous layer closely adherent to the inner surface of layer I and is composed of mucoprotein and acid mucopolysaccharide.

Layer III is made up of three separate sublayers, the relative widths of which vary in different regions of the cyst. In general IIIa consists of mucoprotein, IIIb of acid mucopolysaccharide and IIIc of neutral mucopolysaccharide.

In the dorsal and lateral regions, layer IV appears to be formed of lamellae held in a protein–lipid matrix. The lamellae are composed of protein stabilized by disulphide linkages.

In the ventral region of layer IV there is a thickened mucopolysaccharide area, the ventral plug, through which the metacercaria excysts.

The relative importance of these resistant layers in providing protection against desiccation, toxic substances and attack by other organisms is discussed.

This work was carried out during the tenure of a Commonwealth Post Graduate Scholarship. The author is grateful to Professor J. D. Smyth and Dr J. A. Clegg for advice and encouragement during the course of this work and in preparation of the manuscript.

Penetration and maturation of Schistosoma mansoni were compared in four strains of mice under controlled conditions, with the C3H as the reference strain. Differences were observed in (1) average numbers of cercariae penetrating, (2) percentage of individual mice penetrated by at least 90% of the available cercariae, (3) worm burdens, (4) maturation of penetrants, and (5) consistency of mice with reference to these characteristics. Criteria 2, 4 and 5 have not been evaluated in this way before.

Best average penetration (47%), greatest consistency, and highest percentage of samples with at least 90% of the cercariae penetrating were in mice of the C3H strain (85%). Of the other strains the Swiss albino strain most resembled strain C3H. Beige and hairless mice were comparatively resistant to penetration since only 60 and 30% respectively of these hosts had at least 90% of the cercariae penetrating. Hairless mice gave the best average worm recovery (23%) and parasite maturation (53%) and beige the poorest (15 and 34%). Mice of the Swiss and beige strains were highly variable in terms of parasite maturation.

The establishment of reproducible differences in infections of hosts at the sub-specific level provides basic information for investigation of factors which influence penetration and maturation and which are thus involved in host specificity and innate resistance in closely related animals.

The authors are grateful to Dr Margaret Deringer, National Cancer Institute, National Institutes of Health, for the hairless mice and to Mildred Walters, Naval Medical Research Institute, for assistance in the production of cercariae.

An account is given of the incidence and intensity of infection of the gulls Larus argentatus Pont., L. fuscus L., and L. marinus L. with Cestoda on the coast of Wales. Eleven species of cestodes were found in the three species of gulls, nine in L. argentatus, eight in L. fuscus and six in L. marinus. Nine new host records and two new British records are listed.

The presence of the cestode parasites did not appear to be harmful to the birds.

Ecological and systematic notes are given on each of the cestode species. The basic cestode fauna of L. argentatus, L. fuscus and L. marinus on the coast of Wales comprised three species, namely Tetrabothrius cylindraceus (Rud.), T. erostris (voennberg) and Anomotaenia micracantha (Krabbe).

The factors influencing the intensity and incidence of infection are considered and it is concluded that infection is determined mainly by the food and feeding habits of the host. It is shown that the number of cestodes per bird may be represented by a negative binomial distribution. There is some evidence to suggest that high intensities of infection were associated with high incidences. Three main stages in the development of the helminth-fauna of gulls are described and are related to the age and activity of the bird.

It is a pleasure to record our personal thanks to those to whom we are indebted, namely the Nature Conservancy and the West Wales Naturalists' Trust for permission to work on Skomer Island, to Mr D. R. Saunders, Warden of Skomer Island, for help in the collection of some of the Great Black-backed Gulls, to Mr P. Hope Jones who collected the gulls from Malltraeth, and to Professor J. G. Baer, Departement de Zoologie, Université de Neuchâtel, Professor W. E. Kershaw, Department of Parasitology and Entomology, University of Liverpool, and Mr Stephen Prudhoe, British Museum (Natural History), for the loan of specimens, and to Mr M. D. B. Burt, Department of Natural History, University of St Andrews, for identifying the specimens of Paricterotaenia paradoxa.

The participation of one of us (M. P. H.) in this work was made possible through the generous assistance of a D.S.I.R. research studentship, which is gratefully acknowledged.

Schistocephalus plerocercoids in the weight range 2–200mg F.W. recovered from the perivisceral cavity of Gasterosteus aculeatus were cultured in various media. In a medium composed of 25% horse serum, 0·5% yeast extract, 0·65% glucose and Hanks's saline at pH 7·1, 21°C, 95% air +5% CO2, dry weight increases of up to 500% were recorded in 8 days. The specific growth rate of large plerocercoids was only one-tenth of the rate observed in small plerocercoids. A plerocercoid of double the weight of another had approximately half the specific growth rate.

Worms after 8 days cultivation were found to have only slightly higher than normal glycogen and water content, and to be able to mature when heated to 40°C. However, the rate of growth slowed to zero by the 24th day in culture at 21°C. Electron microscopic examination showed a ‘deposit’ formed over the microvilli, thin at 8 days but dense after 21 days.

The in vivo glycogen and water content of plerocercoids from 3–300 mg F.W. was determined. Glycogen rose from 24% in plerocercoids of 10mg F. W. to 50–55% in plerocercoids over 80mg F. W. The water content was found to mimic precisely this change, falling from 82% to a plateau of 67–69%.

We wish to thank Professor Gareth Owen for permission to use the photograph shown in the Plate and for his help while using the electron microscope. It is also a pleasure to thank Miss Patricia Grant for her technical assistance.

The simple cylindroid pharynx of Ascaris lumbricoides has been shown to be characterized by a pharyngo-intestinal valve which is composed of two sets of valves. This is the only valve structure in the pharynx of this nematode. The pharynges of Oxyuris equi, Aplectana brevicaudata and Panagrellus silusiae have a series of valve structures along the lengths of the organs. All these types have a valve at the anterior end of the corpus, corrugated ‘valves’ in the posterior bulb, and pharyngo-intestinal valves. A valve between the corpus and the isthmus has been shown in Oxyuris.

In all the nematodes studied the pharyngo-intestinal valve is characterized by an overlapping of the muscle fibres associated with the valve and the main musculature of the pharynx that immediately precedes them. It has been suggested that the pharyngo-intestinal valves of the types studied may have evolved from the type of valve found in the Enoplina.

The marginal tissues of the pharynx of Ascaris lumbricoides have been shown to be composed of three types of tissues. It has been suggested that the marginal tissues have a suspensory and skeletal function. The suspensory strands subserve the first function, while the investing strands and the associated fibrous layer provide a longitudinal skeletal structure in the pharynx. In Oxyuris no fibrous layer is associated with the marginal tissues.

I would like to thank Professor J. E. Harris and Dr H. D. Crofton for their help and criticism during the course of this work, which was carried out during the tenure of a Postgraduate Studentship awarded by the Agricultural Research Council.

Four species of the genus Capillaria—C. anatis, C. bursata, C. caudinflata and C. obsignata—are described from the domestic fowl. C. bursata constitutes a new species record for Britain. Taxonomic problems concerning these species in particular, and of Capillaria species in general, are discussed in the light of experience gained from the present study.

This work was carried out during the tenure of a British Egg Marketing Board research studentship and is part of a thesis accepted by the University of London for the Ph.D. degree. My thanks are due to the director of the Houghton Poultry Research Station for granting facilities for work and to the staff for their help and encouragement. Mr R. A. Avery kindly supplied me with material collected from the Wildfowl Trust, Slimbridge.

Male rats were more susceptible than female rats to experimental infection with Amplicaecum robertsi. This sex difference first appeared at the time of puberty, i.e. about 50 days of age.

Suckling rats were less susceptible to infection than weanlings. This was attributed to the cumulative effects of intestinal structure, the indirect effects of milk on the physio-chemical factors in the gut, and the direct effects of milk on the worms themselves.

The rat showed an age resistance to A. robertsi: this was greatest in the female host.

The larvae recovered from females were shorter than those recovered from male rats except in immature animals.

The longest larvae were recovered from suckling rats: in old rats the length of the larvae recovered became progressively shorter as the animals aged.

This investigation was carried out during the tenure of a Senior Research Fellowship from the Wool Research Council of Australia. I should like to thank Professor J. F. A. Sprent for his help and Mr C. Wilkinson for his technical assistance.

The small intestine of rats was divided into twenty sections in a reproducible manner in order to study the distribution of Nippostrongylus brasiliensis by stretching it under a tension of 5g in adrenaline saline.

A small but significant difference between the distribution of parasites in male and female rats was observed.

As larvae had virtually ceased to reach the intestine by the fifth day all changes in distribution after that day were due to movements of the established adult population.

Up to the twelfth day of a primary infestation the majority of the worms were found between the third and tenth sections, the population mode being in the fifth or sixth section. After the thirteenth day the number of worms in this region fell sharply.

The female worms had not ceased from egg-laying by the time most of the worms were being rejected.

The posterior half of the small intestine, i.e. the eleventh to twentieth sections, was not heavily parasitized, many of the worms seen being in passage to the anus.

The first section was not parasitized until the seventh day, but thereafter remained parasitized until long after worms had disappeared from the more posterior sections.

The relative number of male worms present increased as the infestation aged.

Throughout the experiment the relative number of male worms present at the anterior end of the smaller intestine was higher than that at the posterior.

Fourth-stage larvae were found chiefly in the sections that were later most heavily parasitized by adult worms.

Immunity to N. brasiliensis in rats is stimulated primarily by the adult worms. An initial infection consisting solely of adult worms terminated at the same time as an infection consisting of all the parasitic stages.

Immunity is not stage specific. Immunity stimulated by adult worms acts not only on adult stages inhibiting their reproduction but also inhibits the development to maturity of larvae in a challenge infection.

Rats infected solely with female adult worms, whether egg producing or sterile, are more resistant to reinfection than rats infected with male worms only.

Immunity stimulated by a single normal infection lasts a long time but it does not depend on the persistence of adult worms in the intestine of the rats.

This work was done during the tenure of a Commonwealth Scholarship awarded by the Association of Commonwealth Universities.

When rats infected with Moniliformis dubius were dosed orally with labelled sodium phosphate considerable quantities of 32P were found to have been absorbed by the gut-mucosa of the rats and the tissues of the parasites. When the rats were dosed intraperitoneally considerable quantities of 32P were found in the gut-mucosa of the rats but only small quantities in the tissues of the parasites. Similar results were obtained when the experiment was repeated using labelled L-leucine 14C in place of the phosphate and estimating 14C in place of 32P.

The available evidence indicates that M. dubius depends for some of its food-requirements on the contents of the gut of its host rather than on the tissues of its host.

Preliminary experiments showed that the rate of uptake of L-leucine 14C by M. dubius in vitro was decreased if one of the following amino acids were present: DL-valine, DL-serine or DL-methionine.

The author wishes to thank the Department of Biochemistry of the University of Adelaide for the assistance given to him with the experiments on the estimation of 14C.

Observations are described on Polymorphus minutus in its final and intermediate hosts from a wildfowl reserve in Kent. The appearance of the parasite in the reserve followed the alteration of the course of the River Darent, an operation which created a suitable habitat for the intermediate host, Gammarus pulex.

The parasite has been found to occupy the same region of the intestine in the Mallard as in domestic ducks, but it occupies a more anterior region in the Tufted Duck. Worms of varying age have been shown to be present in natural infections of wildfowl.

P. minutus and a cestode, Dicranotaenia coronula, appear to compete for attachment sites in the intestine of Mallard. This competition may be a factor which causes the attachment zone of P. minutus to be extended anteriorly.

The presence of the parasite in the reserve appears to be causing the population of G. pulex to decrease.

It is suggested from the observations made on the birds of the reserve, from the results of infecting domestic ducks and from a consideration of the list of final hosts of the parasite, that there exist strains of P. minutus, adapted to development in different species of birds.

We wish to thank Dr P. Tate for helpful discussions, and Dr I. C. Williams, Department of Zoology, University of Hull, for the identification of the cestodes and criticism of the manuscript. Thanks are also due to Drs J. M. and D. L. Harrison, Mr G. Wallis and Mr A. Meikle for assistance with the population studies and the collection of some of the material.

The body wall of Polymorphus minutus has been studied with the electron microscope and the structure of the various layers has been described.

The layers are the same in number as those seen with the light microscope, and pores have been found which penetrate the cuticle. Thus, the structure of the surface layers is such as would facilitate the absorption of nutrients.

It has been found that the cuticle and striped layer extend over the trunk spines, a feature which increases the area of the absorptive surface of the parasite.

The structure of the striped layer of the praesoma supports the theory that the praesoma body wall and lemnisci are involved in the absorption of fat.

Mitochondria have been detected in the felt and radial layers of the body wall and in the circular and longitudinal muscles.

The body wall of this acanthocephalan worm is entirely different from the body wall of trematodes, cestodes and parasitic nematodes.

We are grateful to Dr P. Tate for helpful discussions, Dr R. J. Skaer for criticism of the manuscript and to Professor J. D. Boyd for permission to use the electron microscope in the Department of Anatomy. Thanks are also due to Mr A. J. Page for technical assistance.

Cells of six isolates of Trypanosoma lewisi from the United States, England, Puerto Rico, Costa Rica, and Singapore were matched against antiserum to the ‘L’ isolate in microagglutinin chambers. Antisera were prepared in Sprague-Dawley rats. Serum protein determinations were made by the biuret reaction; electrophoretic fractionations of serum proteins were done with a semi-closed horizontal system (Evans & Stirewalt, 1947) at 4°C for 24 h, 120 V, and 8 mA with paper strips. Electrolyte was veronal buffer, pH 8·6 and μ 0·058. Agglutinin absorptions were carried out using inactivated anti-‘L’ sera.

Total protein (mg/ml) values were higher in all infected animals (60 vs. 54). Albumin values (%) were higher in controls (47 vs. 40);α-1 fractions were essentially unchanged (15%) as were α-2 values (6%). β Fractions were elevated in infected groups (21 vs. 17%), as were the γ globulins (19 vs. 12%).

Three protocols employing agglutinin reactions were completed. In two protocols 3+ agglutinin end-points were obtained with four isolates using 1·45–1·47 μg of immune γ globulin. Two of the isolates (Puerto Rico and Singapore) required 10 times this amount of immune globulin for the same end-point. In two other tests all isolates gave reaction end-points that required greater quantities (by a factor of ca. 500) of immune γ globulin than obtained in the first two tests, and there was further evidence that the Costa Rican isolate was quantitatively different from the others. These facts are interpreted to mean that all six geographic isolates show close qualitative relationships to each other, but that the relationships for the Puerto Rican, Singapore and Costa Rican isolates are quantitatively different. Agglutinins could not be absorbed from immune serum by any of the cells.

The failure of Boophilus microplus to be cleansed of Babesia bigemina while the ticks were growing on non-bovine hosts, as well as the infection of the non-bovine hosts, was demonstrated in experiments in which infected ticks were released on a number of sheep, a goat and a horse.

Seven of ten batches of ticks, collected from six non-bovine hosts, retained their babesia-infection.

Blood subinoculated into cattle from seven of nine sheep and from the horse showed that these animals carried B. bigemina whilst the ticks were feeding on them. This suggested that ticks may have become reinfected from the non-bovine hosts, a possibility supported by the finding of B. bigemina in blood smears from two of the sheep.

This work was performed at the Animal Research Institute, Yeerongpilly, and in the Department of Parasitology, University of Queensland, and supported by funds from both organizations. I am indebted to Mr G. D. Daly for technical assistance, to Professor J. F. A. Sprent and Dr H. M. D. Hoyte for their interest and help.

Pathological manifestations occasioned by mites of the genus Demodex are reported from Antechinus stuartii, a marsupial mouse. Derangements from single mite invasion of a hair follicle to massive nodule formation are detailed. In heavy infestations mites are found well distributed in the skin of the body with nodules limited, however, to the head, hind legs, around the base of the tail, the cloacal regions and, in females, just anterior to the pouch area.

Mites invade the hair follicle, where increase in their numbers leads to hypertrophy of the follicular epithelium which forms marked lobules surrounded by heavily vascularized connective tissue. It is thought that destruction of the lobule cells and penetration of the blood vessels due to increased mite numbers and activity leads to leucocytic infiltration with destruction of the mites and nodule deflation. In two instances of nodule deterioration a thickened skin plaque with markedly reduced mite populations remained in place of the nodule.

Gross symptoms of demodicidosis are occasionally marked in animals maintained in the laboratory but have not been found in specimens from the field. This suggests that environmental or dietary factors may be important in the onset of gross symptoms of demodicidosis.

This investigation was supported in part by a National Science Foundation (U.S.A.) grant (G-23321) and by a Commonwealth Scientific and an Industrial Research Organization (Australia) grant for marsupial research to the Zoology Department, A.N.U.

Dr Herman Beerman, Professor and Chairman, Department of Dermatology, Graduate School of Medicine, University of Pennsylvania, very kindly read and criticized our interpretation of the pathology. We are grateful for his help.

We would like to thank Margaret Dahlquist, Research Assistant, for her excellent technical assistance in the preparation of material for this report.

Nosomma monstrosum was originally described from a male specimen under the name of Hyalomma monstrosum by Nuttall & Warburton (1908), and the female was described some ten years later by Warburton (1918). Three other males were also seen by him at this time, and he was somewhat hesitant to assign these ticks to the genus Hyalomma. The genus Nosomma was proposed by Schulze (1919) to accommodate this monotypic species, but this appears to have been done without seeing the species and his reasons for establishing the genus appear to be insufficient. Chodziesner (1924) and Sharif (1928) concur on the validity of the genus and the latter defines the genus as follows: ‘eyes flat, scutum, legs and dorsal surface of the capitulum ornate, festoons present, palps short and broad, basis rectangular dorsally in both sexes, coxae I bifid, other coxae with two short spurs on each, ventral shields in the male represented by adanal, accessory and trilobed subanal shields; spiracles short, comma-shaped in the male and subtriangular in the female’. Delpy (1936) agreed in the separation of Cosmiomma and Nosomma from Hyalomma, and in respect of Nosomma stated that ‘Caractérisé par des palpes dont l'article III est plus large que long et par des ecussons subanaux tres volumineux’. Generic status was also accepted by Toumanoff (1944) and Santos Dias (1954).