The capillariid nematodes present in avian hosts collected in Palawan and Borneo are recorded and described. Three new species are established, Capillaria javanensis from Dinopium javanense everetti, Drycopus javanensis hargitti, Mei-glyptes tukki tukki and Megalaima chrysopogon chrysopsis, Capillaria pitti from Pitta sordida sordida, Copyschus niger niger, Copyschus saularis and Chalcophaps indica indica, and Capillaria anthracocerosi from Anthracoceros marchei. Capillaria tridens and C. madseni are recorded from new hosts.

We wish to acknowledge the field support by Dr D. S. Rabor, Department of Biology, Silliman University, Damaguete City, Negros Oriental, Republic of the Philippines, and the technicians of the Parasitology Department of Naval Medical Research Unit No. 2 for general assistance in procurement and examination of hosts. The authors are indebted to Messrs H. G. Deignan (deceased) and George Watson, U.S. National Museum, Washington, D.C., as well as to Dr Rabor for identification of hosts. Dr B. J. Myers assisted with the initial handling of the spe

Initial work for this study was supported by funding under Public Law 480, Section 104(c), by funds provided by the Bureau of Medicine and Surgery, Navy Department Work Unit MR 005.20–0098, by contract no. NR 103–690/N 0014–66–C 0094, between the Office of Naval Research, Department of the Navy and the Southwest Foundation for Research and Education, and grant no. 5 P01-GM-13252–02 from the National Institute of Allergy and Infectious Diseases, DHEW. Final efforts were sponsored by the Department of the Army, contract no. DADA 17–68-C-8094.

Toxascaris versterae sp.nov. from hyenas in South Africa is described. T. versterae is compared with Toxascaris leonina, the only other member of the genus.

I thank Professor J. F. A. Sprent for his advice and criticism. This work was supported by grants from the Australian Research Grants Committee and from the U.S. Department of Health, Education and Welfare, No. AI-07023–03.

A comparative study was made of defined regions of the alimentary tract of third-stage larvae of T. colubriformis and H. placei. The general organization of the tract was similar in both nematodes. The mouth, buccal cavity and oesophagus were lined with cuticle. Muscle cells, apical cells and gland cells were present in the oesophagus. In both species the gland cells contained secretory granules of similar morphology. The lumen of the intestine was ill-defined and apparently nonfunctional. Dense bodies observed in the intestinal cells differed in the two species.

We are grateful to Dr D. W. Brocklesby for his help and advice. We would also like to thank Dr D. L. Lee and Dr W. G. MacMillan for helpful discussions.

Quantitative chromatographic analysis of the free amino acids of the head–foot muscle of uninfected and infected Littorina littorea indicates that there is specific variation in the physiological effects of parasitism. The total concentration of free amino acids in the host head–foot muscle showed an increase of 10·9% with infections of Cryptocotyle lingua rediae, a decrease of 12·7% with infections of Himasthla leptosoma rediae and a decrease of 57·5% with infections of Cercaria emasculans sporocysts. These effects probably depend on three main factors namely, the nature, size and mobility of the larvae of the three species concerned and the influence of these factors in determining the extent of any damage to the hepatopancreas of the host.

The larvae of C. lingua are probably less affected by the changes they induce in the free amino acid pool of the host than the larvae of H. leptosoma and Cercaria emasculans which induce changes equivalent to starvation.

This work was conducted during the tenure of a Science Research Council Studentship. I would like to thank Professor B. John and Mr A. R. Hockley for their helpful advice and criticism.

The frequency distribution of parasites among hosts is used as the basis of the quantitative assessment of the nature of parasitism. The host–parasite system is regarded as an ecological relationship between populations of two different species of organisms. From the overdispersed frequency distributions exemplified by the Negative Binomial distribution a specially truncated form is derived and shown to fit the data of Hynes & Nicholas (1963). The theoretical consequences are discussed and these form the basis of a definition of parasitism.

I am indebted to Professor H. B. N. Hynes who so readily understood my general aims and freely provided detailed information about his work. I also have great pleasure in thanking Professor John H. Whitlock, not only for the original computing facilities which he so generously provided, but also for his many other kindnesses. I am also very grateful to Dr Charles Henderson Jun. for his work on the original computer program and to Dr Mark Westwood for his ingenuity and labours in producing a new approach to the computations.

Serum taken between 2 and 3 weeks after infection of the donors with E. maxima conferred a considerable degree of protection against infection with the homologous organism when injected daily into young recipients. Different pools of such sera had differing activities, but the majority gave protection of 50% or more whereas a few were inactive.

The degree of protection obtained was dose-dependent, varying directly with the volume of serum injected and inversely with the size of the challenge oocyst inoculum.

A course of injections started early in the life-cycle had a greater effect than those started in mid- or late cycle even when comparatively large volumes of serum were given.

Protection was species specific; serum obtained from birds infected with E. maxima did not protect against E. praecox or E. acervulina.

The assistance of Mrs Patricia Hesketh is gratefully acknowledged, as is the help of other members of the staff of the Parasitology Department. Mr P. Townsend, Senior Poultry Attendant, supervised the cleaning and sterilization of cages and the collection of faecal samples.

Tissue stage and erythrocytic stages of a new malaria parasite Rayella hylopetei n.sp., is described from a Particoloured flying squirrel Hylopetes alboniger Hodgson encountered in Darjeeling. Tissue stages are represented by schizonts in the form of cystic bodies occurring in characteristic foci of infection occurringi n the liver. Schizonts are absent in the erythrocytes, and it appears that all immature stages in the erythrocytes directly develop into gametocytes. Haemozoin pigments occur in the form of black granules. The infected red blood cells are slightly enlarged and are without stippling.

The investigation received financial support from the World Health Organization.

Acetylcholinesterase activity, measured per unit wet weight, is relatively low in the eggs and infective larvae of N. brasiliensis. It increases rapidly during the parasitic phase, especially in the late 3rd- and early 4th-larval stages. Activity in normal adults is extremely high (× 15 egg activity) and this is doubled again in immune-damaged adults. Possible functions of N. brasiliensis acetylcholinesterase are discussed.

It is a pleasure to acknowledge the technical assistance of Miss Anne Cronin and Miss Beryl Crooks.

Larval Taenia crassiceps of the ORF and KBS strains have been shown to accumulate whole 14C-Chlorella proteins in the bladder fluid. Precipitation by trichloroacetic acid removed 70% of the radioactivity indicating the 14C-Chlorella proteins had not been catabolized during movement into the bladder fluid.

The fine structure of the macrogametocyte, macrogamete and the early stages in the formation of the oocyst wall of Eimeria acervulina have been described and compared with other species of Eimeria. It has been shown that type II wall-forming bodies are formed in cisternae of the granular endoplasmic reticulum in association with Golgi complexes. The developing oocyst has been shown to be enclosed by three membranes: the outermost is the original membrane of the merozoite and macrogametocyte; the second membrane appears when the wall-forming bodies are appearing in the cytoplasm of the macrogametocyte and the innermost membrane appears after fertilization. The wall-forming bodies discharge their contents between the innermost membrane and the middle membrane.

We wish to thank Mr P. L. Long for much valuable discussion, Mrs B. Fisher for technical assistance and Mr B. Carter for assistance with the photography.

A new trematode, Burnellus trichofurcatus, is described from South Australia from the freshwater catfish, Tandanus tandanus. It appears to have affinities with Monodhelmis Dollfus, 1937 and Mehratrema Srivastava, 1939, but is probably most closely related to Tandanicola Johnston, 1927 (Fellodistomatidae: Tandanicolinae). It is assigned to the Fellodistomatidae Nicoll, 1909, as emended by Cable (1953). Cercaria trichofurcata Johnston & Angel, 1940 is shown to be the larval stage. The cyst stage is omitted from the life cycle, with infection of the catfish occurring directly, probably by mouth. Further comments on developmental stages are given. The sporocyst is not branched, as described by Johnston & Angel (1940). The miracidium of Tandanicola bancrofti is reported, and the life history of this species is discussed. The genus is named for Dr R. H. Burnell in recognition of his help, over a number of years, in collecting animals used in these life history studies.

I would also like to acknowledge information and help given me by Dr J. C. Pearson, of the University of Queensland, and information on fish given me by Mr C. J. M. Glover, of the South Australian Museum.

In order to learn more about the nature of the chemical bonds stabilizing the surface membranes of the cercariae and schistosomula of Schistosoma mansoni, these organisms were treated with a variety of reagents. The cercarial surface was dissolved by 8 M urea alone (pH 9·0) but was protected from such dissolution if a certain critical concentration of cation or anion was included in the 8 M urea solution. Divalent cations were more effective than monovalent cations in this protective effect. The 8 M urea was also unable to dissolve the cercarial surface at any pH below 5·8. The cercarial surface was very rapidly dissolved by sodium hydroxide solutions at pH 11·4 and above. The divalent cation calcium, if included in the sodium hydroxide solution, slowed down the rate of surface solution by sodium hydroxide. The schistosomular surface was stable to 8 M urea at pH 9·0 but was readily dissolved in 8 M urea at pH 10·7 and 11·7. The schistosomular surface was stable in aqueous sodium hydroxide solutions at pH 12·0. Anionic detergents were very effective in dissolving the cercarial surface at concentrations above 0·001%. Cationic and non-ionic detergents were ineffective at 0·01% or below. A saturated solution of digitonin if diluted 1:100 caused destruction of the cercarial surface. At higher concentrations it caused expansion and stabilization of this surface.

It is suggested that in both the cercarial and the schistosomular surface, bonds between carboxyl (—COO′) and amino (—NH3+) groups are very important in maintaining structure. The origin of the —NH3+ group is possibly from —NH2 lysyl group in cercariae, and a guanido group in schistosomula. The suggestion that cations are incorporated into the cercarial surface and stabilize it during and after penetration has been tested by treating schistosomula with EDTA. The EDTA had no visible effect on the surface, nor did it labilize the surface to other reagents.

I should like to thank very warmly Dr S. A. Ibrahim, in whose Department this work was carried out. My grateful thanks are given to the Medical Research Council (U.K.) for a grant. I should also like to thank Mr J. R. Lauder, Mr Ahmed Gandour and Mr Saleh for their help during the work. I am very grateful to Dr J. A. Clegg and Dr S. R. Smithers for helpful discussions.

Microspines 0·05 μm long and 0·002 μm in diameter at the base have been demonstrated on the egg shells of S. japonicum. They are protrusions of the shell but are structured into inner and outer layers of differing electron density.

Spines observed on the shell of S. haematobium can be flexed by contact with host cell membranes. Firm, perhaps binding, contact is suggested. The spine length serves to define a space between the shell wall and the host cell membrane which could represent the primary interface of host parasitic contact.

The base compositions of DNA from some species of malarial parasite have been estimated by measurement of density in CsCl gradients and of thermal denaturation temperatures. Species from avian (Plasmodium gallinaceum) and rodent (P. berghei and P. vinckei) hosts – often used as model systems in malarial studies – contain single DNA components with base compositions of about 20% G + C. By contrast, species from primate hosts (P. knowlesi and P. falciparum) contain major DNA components of about 40% G + C and minor ones of about 20% G + C. These differences could be reflexions of markedly different genomes within these two groups of the genus Plasmodium.

Apart from differences in base composition, the physico-chemical properties of the main components of DNA from primate and rodent malarial parasites are very similar to those of DNA from mammalian cells. DNA from avian malarial parasites appears to have some unusual properties.

One of us (P.I.T.) received financial assistance from the World Health Organization. We thank Dr F. Hawking and Dr J. Williamson for many helpful discussions, Dr W. H. G. Richards, Dr A. Voller and Dr D. C. Warhurst for the provision of some of the strains and Miss Jane Dunnett, Mrs A. C. Gutteridge and Mr T. Scott-Finnigan for technical assistance.

The mature egg and the acanthor of Moniliformis dubius have been redescribed with special emphasis on the features relevant to the locomotion of this larval acanthocephalan. The movements of acanthors have been analysed by the use of frame by frame study of filmed records of motile acanthors. Acanthors appear to use the same mode of locomotion for hatching, locomotion within the gut of the intermediate host and penetration of the host's gut wall. Movement is produced by a set of spiralled, longitudinal muscles in the body wall of the hind body and two rostellar retractor muscles. This musculature acts both directly on the body wall and indirectly by hydraulic effects via the hydrostatic skeleton of pseudocoelomic fluid. The spiny evertable rostellum and the backward facing spines of the hind body are the means whereby shape changes of the acanthor interact with the immediate environment to produce effective progression.

I should like to thank Professor D. Arthur for the provision of laboratory facilities, Dr D. W. T. Crompton for the initial gift of eggs of M. dubius and Mr R. D. Reed for invaluable assistance with microcinematographic technique. The work was carried out during the tenure of a Nuffield Foundation Research Fellowship.

Three male and four female parasites were recovered from the gizzard of a koel, Eudynamys scolopacea Linnaeus (Cuculiformes). In all, about forty birds were examined and only one was found infected. The present account is based on a study of three male and three female specimens, one female specimen being slightly damaged.

The host-specificity of monocystids was investigated experimentally by infesting infection-free Dendrobaena subrubicunda f. typica with sporocysts of Apolocystis megagranulata and A. lavernensis normally found in Dendrobaena subrubicunda and Allolobophora longa respectively. An attempt to infect worms raised free from infection with sporocysts of Monocystis agilis normally harboured by Lumbricus spp. was unsuccessful. Eighteen of the thirty identified monocystids were found to be monobiotic (species-specific), eleven were oligobiotic (genus-specific) and only one was polybiotic (family-specific).

The writer wishes to express his sincere appreciation to Dr Anne Terry for her advice and useful suggestions, and to Mr D. Etherington, the head of department, for his encouragements throughout the research period.

Babesia rodhaini infected mouse and rat red cells were non-infective after receiving 40 or 60 krad irradiation from a 60Co source.

Rats inoculated with irradiated infected red cells were subsequently found to show strong resistance to homologous challenge.

Mice, which are more susceptible to B. rodhaini, showed less resistance to challenge, following immunization with irradiated B. rodhaini infected red cells.

Splenectomized rats were immunized with irradiated infected blood. There was a delay compared with the controls in the onset of acute fatal parasitaemias in these rats. A population of parasites was isolated by taking and mixing blood from each of the splenectomized rats during the patent parasitaemia following challenge. This population appeared to be an antigenic variant of the original immunizing population.

I thank Mrs J. Page for excellent technical assistance and Dr K. N. Brown for criticizing the manuscript.

The structure of the cysticercoid of Raillietina cesticillus has been studied with the aid of light and electron microscopes. While the ultrastructure of the superficial parts of the scolex closely resembles that of other cestodes, the fine structure of the cyst wall differs from both these. The arrangement and functions of the tissues in the cyst wall are discussed and interpreted with reference to the tissues of the scolex of the cysticercoid of R. cesticillus and to the tissues of other cestodes. R. cesticillus cysticercoids, subjected to various histochemical tests, were shown to contain proteins and carbohydrate materials.

The author wishes to thank the Principal and Governors of West Ham College of Technology, a constituent college of the North-east London Polytechnic, for their general and financial support of this work. Thanks are also due to the Directors and Governors of the several institutions whose electron microscopes the author used. The work described here forms part of a thesis approved by the University of London for the degree of Ph.D.

African representatives in the family Microphallidae (Trematoda) are recorded, and descriptions of five new species are given. Collections made on the Kenya coast showed: (Aves) Crocethia alba infected with Microphallus kenyensis sp.nov.; Encocotyle africanus sp.nov., and Maritrema sethsmithi sp.nov.; Tringa hypoleucos and Numenius phaeopus infected with Diacetabulum curvicolon Belopolskaia, 1952; (Reptilia, Scincidae) Ablepharus boutonii africanus infected with Levinseniella heardi sp.nov., Maritrema sethsmithi sp.nov. and Maritreminoides ablephari sp.nov.

Patti Hirst and Alma Smith assisted with preparation of the plates. R. W. Heard III and S. Deblock loaned material and made helpful comments on the reproductive structures in the genus Levenseniella.