The host of this gregarine is Dacne rufifrons Fabr., a small beetle, which is commonly to be found feeding on the polypores which grow on old elm trees in the neighbourhood of Cambridge. Beetles collected in the Autumn, and again in the following Spring, were very heavily parasitized. The beetles live together in small colonies, a habit which greatly increases the chance of infection.

The systematic position of Nematodes is an old standing problem which has already received much attention from zoologists. The conclusions at which they have arrived are however very discordant and the most widely separated orders of Metazoa have been claimed as near relatives of Nematodes. This great divergence of opinion has not abated the general interest in the problem, but, on the contrary, has had a greatly stimulating effect as was shown recently at the British Association for the Advancement of Science (1923) in a discussion on the affinities of Nematodes, opened by Prof. Hickson and supported by Prof. Goodrich and Dr Baylis. The results of this discussion were soon afterwards incorporated by Dr Baylis in a very interesting paper containing a complete review of the problem as well as a statement of the author's own views.

The animal under consideration belonging to the family Lernaeopodidae was taken on a codling (Gadus morrhua), 13 ins. in length, caught at Plymouth several years ago, and preserved in formalin since that date. Although about twenty-six valid species of Clavella have been either recorded or described in detail, the subject of the present paper differs from them all in combining several of the more prominent characters of other species, notably the extreme length of the backwardly-arched cephalothorax taken together with the reduction of the “arms” (second maxillae) and their expansion into a disc so that the “bulla” or button appears to be almost directly affixed to the body. For this species I accordingly propose the name Clavella sciatheric.

In 1909, Professor McIntosh of St Andrews University sent me a cyst from the abdominal cavity of a South African baboon, Cynocephalus porcarius Budd. The cyst, which was single, had been ruptured in removal, part of its contents had escaped, and some blood had entered it. The cyst measured about 20 mm. in diameter, was a typical hydatid, and resembled in its general structure the ordinary simple unilocular hydatid of man.

Eight forms, referred to the genus Ascaris, were described by Dr W. Baird between 1853 and 1868, all of which are represented by type-specimens in the British Museum collection. Stossich, in his monograph of the genus Ascaris (1896), mentions six of them, but all these are regarded by him as species inquirendae. Baird's descriptions are in all cases brief, and confined almost entirely to external features, this rendering them inadequate for the requirements of present-day systematic workers. I have, therefore, thought it advisable to undertake a revision of the various types, with a view to deciding more definitely their systematic value, and, where possible, to re-describe those which appeared to me to represent valid species.

Since its discovery in France by Mégnin (1878), Cheyletiella parasitivorax has been found in many countries—on rabbits (Oudemans, 1906; Pillars, 1925; Ford, 1944; Mykytowycz, 1957a; Womersley, 1941), on the dog (Humphreys, 1958), fox (Kuscher, 1940), cat (Niggli & Teuscher, 1959; Davies, 1941), man (Olsen & Roth, 1947) and even in phoretic association with fleas (Cooper, 1946). Hirst (1917) was the first to find the species in Britain and there have been several more recent records from this country.

Cytamoeba bacterifera from urodeles (Batrachoseps attenuatus, Aneides lugubris, A. flavipunctatus and Dicamptodon ensatus) show a thin peripheral ring of DNA and a less definite, heterogeneous central portion after Feulgen treatment; toluidine blue reveals a similar configuration. Exposure to DNA-ase and RNA-ase, followed by toluidine blue and Feulgen treatment, substantiates the localization of DNA; RNA is present in small quantity and restricted to the periphery of the parasite.

Mitochondria (2–5μ long rod-shaped, central bodies) can be detected with Janus Green B, and osmium tetroxide yields a dark central mass of rods and granules as well as peripheral granules; Sudan Black IV is without action. Zymohexase and acid phosphatase can be detected by cytochemical means, but peroxidase, lipase, urease and alkaline phosphatase were not noted.

From the evidence presented, C. bacterifera is considered a living entity and is tentatively relegated to the Piroplasmida.

The writer would like to express his appreciation to Dr R. S. Bray of the American Foundation for Tropical Medicine, Harbel, Liberia, for his counsel and suggestions.

The structure of the intestine of adult Nematodirus battus is described. It is similar tothe intestine of some other trichostrongyles but with a few minor differences. Changes in the structure of the intestinal cells are described in N. battus taken from lambs during the later stages of an infection (days 20 to 32) with 60000 infected larvae. The mostnoticeable changes were a decrease in the amounts of glycogen and smooth endoplasmic reticulum, a reduction in the numbers of secretory-type granules and the appearance of vacuoles within the cells. Some of these vacuoles contained small crystals, and crystals, some of them large, were also found in the intestinal lumen. These changes, with the exception of the appearance of the crystals, are similar to changes described for Nippostrongylus brasiliensis affected by the immune response of the rat host, and it is concluded that the changes in N. battus could have been initiated by an immune response to this nematode in the lamb. Lambs given 2000 larvae of N. battus do not reject the nematodes in 32 days, and no changes were observed in the structure of these nematodes.

All instars of the pentastomid Porocephalus crotali, in the tissues of rat intermediate hosts and the lung of rattlesnake definitive hosts, are covered by a vesicular or stacked membranous secretory product which is synthesized in sub-parietal cells (SPC) and channelled to the cuticle via multitudinous chitin-lined ducts. In rats this enveloping foam of vesicles survives for the duration of a cuticle. We have purified and partially characterized the lipid and protein composition of lamellate droplets from SPC of infective nymphs. Lipids in the droplets comprised a mixture of neutral and polar lipid classes with cholesterol being the major neutral lipid and phosphatidylcholine the dominant polar lipid. In addition, Triton X-114 phase separation of the protein component of droplets partitioned these into an aqueous phase (with a major band at 60 kDa), a detergent phase with two hydrophobic polypeptides (24 and 16 kDa) and an insoluble pellet containing several minor proteins and major bands at 31 and 107 kDa. Western blotting, with rabbit anti-lamellate droplet antiserum, strongly label only the 60 kDa and the two hydrophobic proteins. Significantly no proteins at all label with serum from infected rats from 50–150 days post-infection, a finding endorsed by indirect fluorescent antibody tests on sectioned V–VII stage nymphs. Possible immunomodulatory functions of SPC-derived surface membranes are discussed and, in this regard, they are compared with pulmonary surfactant, a product of alveolar Type II cells which lines all vertebrate lungs.

The percentage change in weight, at 38·2 °C, in different concentrations of sodium chloride at different intervals, of a trematode, Gastrothylax crumenifer, from the reticulum of buffaloes has been recorded.

A state of approximate isotonicity is reached between 0·4 and 0·5% sodium chloride.

The osmotic pressure has also been expressed in terms of freezing-point depression.

An in vitro culture of Plasmodium falciparum (isolate FCUP-1/RSA) was arrested in the trophozoite stage with α-difluoromethylornithine (DFMO), followed by sorbitol treatment to liberate intracellular parasites from infected erythrocytes. Most of the unlysed erythrocytes and ghost membranes were removed by filtration, after agglutination with anti-erythrocyte monoclonal antibodies or wheat-germ agglutinin. A highly purified parasite preparation was obtained after chromatography on an immuno-affinity column consisting of polystyrene particles to which anti-erythrocyte monoclonal antibodies had been adsorbed. Isolated parasites were free of surrounding erythrocyte membranes and structurally intact as assessed by transmission electron microscopy, SDS–PAGE and ELISA.

Cysteine (20–100 mM) and reduced glutathione (20–80 mM) potentiated the development of the exsheathed third-stage larva of Haemonchus contortus to the fourth stage. The potentiating effect of cysteine was greatest during the short period before and after the exsheathment of the third-stage larva. Two hundred mM cysteine and 1 mM p–chloro-benzoate inhibited development. This inhibition was reversible. Ten mM iodoacetate and 0·5 and 5 mM n–ethyl-maleimide inhibited development of the larvae. The larvae appeared to be most susceptible to the inhibiting effects of these reagents during the period of development approaching the third moult. Development was either little affected or potentiated, when larvae were incubated with these reagents for short periods immediately after exsheathment.

Two types of exflagellating bodies of the malaria parasite are described in the infected blood of the Himalayan flying squirrel (Petaurista magnificus). The first type, which is larger, is characterized by a blue-staining cytoplasm. These produce blue-microgametes with red chromatin dots. The second type, which is smaller, stains red, and also produces red microgametes. Certain large schizonts occurring in the peripheral blood are described. It is speculated that these might represent the primary tissue stage of Rayella rayi.

The effects of the phenothiazine, Stelazine, on Hymenolepis diminuta were investigated. The cestode was incubated for 10 min at 37 °C with 1 mM trifluoperazine, in the presence and absence of Ca2+. Assay of brush border enzymes showed that drug treatment lowered the activities of alkaline phosphatase, Ca2+-ATP'ase, 5′-nucleotidase and type 1 phosphodiesterase. This occurred in parallel with a significant reduction in tegumental protein. Under these conditions gross changes in ultrastructural appearance and cellular organization were observed. There was a lack of ordered microtriches and the distal cytoplasm was absent. Glycogen granules were scattered throughout the cytoplasm within the subtegumental layer. The connective tissue also appeared to be in some disarray. The effects of Stelazine appeared to be dependent on time and were significantly increased when Ca2+ was included in the incubation medium. Incubation with the less hydrophobic phenothiazine trifluoperazine sulphoxide had minimal effect on the integrity of the cestode. The results reported here support the premise that certain phenothiazines may be considered as potential cestocidal agents.

Stages seen in the life-cycle of Diplocystis tipulae sp.nov. parasitic in Tipula paludosa Mg., included a structure that was probably a trophozoite within the midgut epithelium of one host larva and gamonts that developed on the midgut wall in the haemocoele of the larvae. Syzygy occurred, usually in pairs, when the gamonts were about 200–300 μm in diameter. Initially, syzygous gamonts were bilobed but they quickly became spherical and were enclosed by a fine membrane to form a gametocyst 450–550 μm in diameter. Early stages of gametogony were seen in one pupa; sporogony occurred in pupae and adults. The mean size of the round–oval oocysts was 7·14 × 6·26 μm. Individuals of Tipula oleracea L. are also susceptible to infection with D. tipulae. This gregarine is considered to be a new species, independent of the gregarines of the gut lumen.

Four-day-old worms of the tapeworms Hymenolepis microstoma, H. diminuta and H. nana and newly excysted H. microstoma were exposed in vitro at 37 °C to immune serum from mice infected for 4–1 2 weeks with H. microstoma. Worms were fixed for electron microscopy after intervals of 5 min to 96 h. Within 10–15 min an homogeneous precipitate occurred between the microtriches of 4-day-old H. microstoma and H. nana, while on some areas of H. microstoma the precipitate extended distal to the microthrix border and contained small vesicles (30 nm in diameter) and shed microtriches. In H. diminuta precipitates were not found until 2 h post-incubation. The thickness of the precipitate and the number of small vesicles and shed microtriches increased with time after incubation. Since a similar precipitate occurred on worms kept in complement-depleted immune serum, antibodies alone may induce immune damage. The precipitate on newly excysted H. microstoma lacked microthrix fragments. After 48 h an extensive precipitate was found protruding from the rostellar glands on some H. microstoma, and within the culture vessel. Antibodies may therefore be complexing with tapeworm secretory products.

It is generally believed that the patterns of in-host migration of the infective stages of most invasive macroparasites of man and domestic animals are matters of established fact. In reality, the textbook treatment of this topic, and much of the experimental approach to it, are a legacy of an uncritical past. With few exceptions the true picture concerning particular host/parasite systems is confused by the acceptance of inadequate criteria of proof. In important instances these bogus ‘proofs’ have been generalized within a suspect inductive framework which employs the basic assumption that all migratory parasites that enter the same portal and travel to the same destination do so by the same route. The discussion of such issues serves as a background to the presentation in detail of a more rigorous conceptual and experimental framework.

Methotrexate inhibited the growth of D. viviparus by acting either on the moult from the third- to the fourth-stage larva or on the growth of fourth-stage larva itself. Despite these effects of the drug, the early developmental stages of the worms primed the immune mechanism of the host; the inductive phase of antibody production was completed in less than 5 days. An effective immune response, however, was blocked by the continued presence of methotrexate which resulted in delayed elimination of a superinfection and the absence of anaphylactic antibody in the serum. Immune elimination appeared to require a quantitative threshold of worm antigen and host antibody.

This work was made possible by the generous supply of infective helminth material from Messrs Allen and Hanbury Ltd, Ware, Herts. I should also like to thank Dr J. H. Humphrey and Dr S. R. Smithers of N.I.M.R. for their helpful discussions.

The tetrad and companion cells, in association with the oesophagus and dorsal tract of tissue, of Tetradonema plicans, have been investigated in the host Bradysia paupera. The companion cells contain glycogen and mucopolysaccharide. The tetrad cells are rich in RNA and probably synthesize protein and secrete some as enzymes. The gut is functional and the oesophagus is in connexion with the tetrad. The dorsal tract is not connected with the oesophagus or tetrad and contains lipid with characteristics similar to that found in the eggs.

It is suggested that the tetrad and companion cells are homologous with the stichocytes present in the Trichuroidea and some members of the Mermithoidea.

I am grateful to Professor T. R. E. Southwood in whose department this work was carried out. I should like to thank Dr N. A. Croll for supervising and encouraging this work and Dr T. Jenkins for his helpful criticism and advice. The work was supported by the Agricultural Research Council.

The proteins in the soluble and membrane fractions of Plasmodium lophurae, separated by SDS-PAGE and stained with Coomassie blue, were distinct from one another and different from the soluble and membrane proteins of the host cell, the duckling erythrocyte. Pulse-labelling of malaria-infected red cells containing schizonts or trophozoites with [14C]isoleucine, followed by parasite isolation, SDS-PAGE and autoradiography, showed a pattern of incorporation into soluble proteins identical to the banding pattern of gels stained with Coomassie blue. On autoradiograms, the banding patterns of the membrane proteins of trophozoites and schizonts labelled with [14C]isoleucine were similar. No qualitative differences in the soluble proteins of trophozoites and schizonts were apparent when isoleucine was used as the radiotracer; however, the banding pattern of membrane and soluble proteins labelled with [14C]isoleucine were distinct from each other. The banding pattern of soluble proteins, after staining with Coomassie blue, was distinctly different from the array of bands seen after autoradiography of parasites derived from infected cells pulse-labelled with [14C]histidine. Only small amounts of contaminating haemoglobin in the soluble protein fraction of parasites were labelled with histidine; the membrane fraction, on the other hand, had high incorporation into a single 43 kDalton band, the histidine-rich protein. No band differences, either in the membrane or soluble fractions, were observed in autoradiograms after pulse-labelling trophozoites and schizonts with [14C]histidine. The most consistent and distinct differences in protein synthesis were seen in P. lophurae pulse-labelled with [14C]proline. Autoradiograms of both soluble and membrane fractions showed the presence of bands unique to the trophozoite and schizont–stage-specific proteins.