Studies have been made of the growth and excystment of a trematode, Acanthoparyphium spinulosum, in chicks fed on various denned diets.

Day-old chicks were fed metacercariae and maintained on deficient as well as complete rations for periods up to 20 days. The excystment rate was determined by the number of worms that were recovered from the metacercariae. The largest number of worms were recovered from chicks that received a normal diet with starch as the sole carbohydrate source. The smallest percentage of parasites was found in birds that had received a normal diet with sucrose serving as the carbohydrate source. About 25 % were recovered from chicks fed several other diets.

The trematodes developed and grew well in vitamin A deficient chicks; there was a large number of intra-uterine ova observed in worms from these hosts. Acanthoparyphium spinulosum from chicks fed a ‘no vitamin D’ diet grew at a normal rate until the 6th day; after this they grew more slowly than 6-day-old worms in chicks fed the ‘no vitamin A’ diet.

The lengths of worms from birds deprived of all vitamins differed little from those of the parasites recovered from the chicks deficient in vitamin D. The largest worms were obtained from chicks fed a complete diet with starch as the sole carbohydrate source.

Parasites from chicks fed a diet 50 % deficient in carbohydrates (with sucrose as the carbohydrate) developed normally.

Worms also developed in chicks fed a ‘no protein’ diet with starch and a ‘no protein’ diet with sucrose. A deleterious effect on ova production was observed in worms from both these groups.

Metacercariae developed in chicks fed a ‘no carbohydrate’ diet, but no mature worms were recovered due to the reduced life of the host. Starvation of the hosts produced small worms containing few intra-uterine ova.

The growth curve of A.spinulosum was plotted and compared with Echino-paryphium flexum.

This investigation was supported in part by U.S. Public Health Service Grant UI-00202, and by a grant-in-aid of research by the Society of the Sigma Xi, New Haven, Connecticut.

The Trematode herein described was obtained from the gills of Trigla hirundo Day, popularly called the Yellow Gurnard, Latchet or Tub, one of the most common species of the Gurnard family found on the west coast of Ireland.

Eperythrozoon mariboi sp.nov. is described from the red blood cells of splenectomized flying foxes (Pteropus macrotis epularius), from New Guinea. The parasite is polymorphic. The most common form is a fine line 5–8 μ long extending across the red blood cell. Marginal forms are also found. Multiple infections of the host cell also occur. In the initial infection ring forms were common, as well as other forms.

Parasitaemia was followed by anaemia, and the infections were characterised by repeated relapses at irregular intervals.

This work was supported by Grant No A1–08449 from the National Institutes of Health, United States Department of Health, Education and Welfare. I would like to thank Mr T. Ikupu and Mr T. Engendi, both of the University of Papua and New Guinea, for technical assistance; Mrs M. Cahill, also of the University of Papua and New Guinea for attempting to culture the organisms; Dr D. Weinman of Yale University, for confirming the identity of the parasites; Dr T. J. Dondero of the Hooper Foundation for translating some of the references into English; and Dr F. Colley also of the Hooper Foundation, for comments on the manuscript.

The analysis of some of the data in this paper was done while I was on study leave at the Institute for Medical Research, Kuala Lumpur, and I would like to thank its Director for the hospitality provided.

I would especially like to thank Mr Yap Loy Fong, Institute for Medical Research, Kuala Lumpur, for preparing Fig. 1.

Using a simple infection model the infection interaction of Steinernema feltiae (Site 76 strain) Filipjev and Galleria mellonella L. was investigated under laboratory conditions. The model analyses showed that the infection interaction was consistent with a proportion of the S. feltiae infective stages being infectious and, alone amongst the infective-stage population, being capable of infection. The investigation also showed that the infection behaviour of the infectious stages could be reduced to a slightly overdispersed probability of transmission. The importance of these findings with respect to the quantitative description and explanation of infection are discussed.

The observations relating to the treatment of canine piroplasmosis by means of drugs are usually very briefly recorded so that the precise conditions under which they were conducted cannot be ascertained.

Fasciola hepatica, a parasitic flatworm belonging to the Class Trematoda, is one of the first metazoan groups to possess a centralized nervous system. However, the electrophysiological properties of neurones in F. hepatica are largely unknown. In the present study, we acutely isolated viable neurones from F. hepatica and characterized their electrophysiological properties. A hyperpolarization-activated cation current was recorded in the cells using the whole-cell patch-clamp. The current was found to be activated slowly at membrane potentials negative to 0 mV and did not display any time-dependent inactivation. This current was reduced by 1 mM Gd3+ to the level of the leak current, while 3 mM of Cs+ had no effect. However, the current was inhibited by extracellular acidosis in the pH range 7.0–7.8, and the membrane potentials of these cells were depolarized by extracellular alkalosis in the pH range of 5.8 to 8.2. Gd3+ (1 mM), which inhibited the pH-sensitive hyperpolarization-activated cation current, also hyperpolarized the cells. In summary, we isolated single neurones from F. hepatica, and these were found to express a pH-sensitive hyperpolarization-activated cation current. This current may participate in the membrane depolarization of F. hepatica neurones during alkaline challenge.

During my stay at the Zoological Station of Wimereux, Pas de Calais, France, in August 1934, I made a special study of Protozoa parasitic in marine fishes. The examination of ten specimens of young Raia batis revealed a coccidial infection in two individuals, measuring about 25 cm. in length. In one of these the mucus in the terminal portion of the intestine contained a few unsegmented spherical oocysts, with diameters from 24 to 28μ. Sections of different portions of the intestine and of the liver failed to exhibit any stages of schizogony or gametogony, evidently owing to the fact that there was a single infection at the end-phase. However, the second skate showed very numerous unsegmented oocysts in the posterior portion of the alimentary canal (Pl. I, fig. 1). This specimen provided material for the morphological study and biological observations which follow.

1. The paper discusses the points of difference between the three larval instars in Pediculus and the changes in proportion which take place during growth, not only during larval life but also at the final moult.

2. It is easy to separate larvae of the first instar from others, more difficult to distinguish those in the second and third instars. The principal points of difference are as follows:

First instar. Setae on dorsum of abdomen, few, long and in longitudinal lines: one median pair on most segments. Paratergal plates (carrying spiracle) absent. Mean measurements as in Table I, the best point of distinction between instars being in length of third tibia, which is 0·197 mm. in first instar. Ratio of head to thorax and abdomen about 1:2·8

Second instar. Setae of dorsum of abdomen in one transverse row, containing 2–3 pairs of setae. Paratergal plates present (as also in third instar). Mean length of third tibia, 0·270 mm. Ratio of head to thorax and abdomen about 1: 3·5.

Third instar. Setae on dorsum of abdomen, not in one row, but somewhat irregular: a pair of minute supplementary setae, on seventh and eighth segments, close to midline. Mean length of third tibia, 0·363 mm. Ratio of head to thorax and abdomen about 1:4·3.

3. During larval life the dimensions of all parts increased as geometrical progressions (Dyar's law), but the rate of increase is different in different parts of the body, so that the proportions, for instance, of head to thorax and abdomen alter with growth; in other words, growth is allometric or heterogonic. But when the insect attains maturity the measurements of several of the parts depart significantly from the geometrical progression which has prevailed during larval life. In most parts of the body the increase at maturity is greater in females than males (no point of distinction having been observed in larvae in the preceding instars); but in the length of the third tibia the increase in the female is much less than in the male. Among other insects in which metamorphosis is slight there are several in which the rate of growth of parts alters at the last moult and becomes different in the two sexes; in some indeed the difference develops much earlier than the last moult. Probably, therefore, it would be true to say that regular allometric growth is generally disturbed by the development of secondary sexual characters.

It is a pleasure to acknowledge help received from Dr J. S. Huxley.

Predation can regulate populations and strongly affect invasion success of novel prey. The deer ked (Lipoptena cervi; Linnaeus 1758) is an invasive ectoparasite of cervids that spends a long period of its life cycle outside the host. Prior to this study, virtually nothing was known about natural summer time predation on the deer ked. We aimed to evaluate the magnitude of summer time predation on L. cervi pupae in different habitats and to identify potential predators. We conducted a set of field experiments, where we exposed L. cervi pupae to various ground-dwelling vertebrate and invertebrate predators. The loss of pupae was monitored for different predator guilds. Three habitats of the moose, the main host species, were studied: (1) moist heath forest; (2) dry, logged heath forest; and (3) moist meadow. The results indicate notable summer time predation on L. cervi pupae, and the pupal predation varied within and between habitats, being lowest in the meadow habitat. We found a positive correlation between pupal loss and abundance of the common lizard (Zootoca vivipara), harvestmen (Opiliones), ground spiders (Gnaphosidae) and Formicinae-ants. We conclude that summer time predation during the pupal phase can have a notable local importance for the L. cervi abundance.

Digenean flukes can be broadly classified into three basic groups according to their location within the host: (1) the lumen of the alimentary canal or associated organ, (2) body cavity or tissue and (3) external surfaces. We selected three species of Proterometra that represent these basic groups and tested their capacities for cutaneous transport of glucose. Facilitated diffusion is the type of transport system in the tegument of P. edneyi, which lives in the gut of its host. An activetransport system is present in P. dickermani, the tissue-dwelling species. No cutaneous system for transporting glucose is present in the ectoparasitic P. macrostoma. The known capacities for tegumental sugar transport in other digeneans are correlated with similar habitats. Such associations involving unrelated as well as closely related species suggest that the niche biology of digeneans involves evolutionary specializations of the tegument for absorbing sugar.

Infective Haemonchus contortus cayugensis larvae were stimulated to exsheath in 0·02 m-Na2B4O7. 10H2O, into which was bubbled CO2. The larvae under the exsheathing stimulus were found to be coiled and sluggish. The larvae became very active after most of the CO2 was removed by compressed air, oxygen or nitrogen. The exsheathment rate in each of the latter instances was higher than when larvae were exsheathed completely in an atmosphere of CO2. Carbon dioxide is an essential component of the exsheathing stimulus, but the continued presence of a high pCO2 or carbonic reaction products appeared to inhibit larval motility and caused lower exsheathment rates.

Les collections de l'lnstitut Pasteur possèdent un assez grand nombre d'exemplaires, à tous les stades, d'un curieux Argasiné recueilli en 1911 par la mission Bouet-Roubaud, au cours de son exploration parasitologique des régions soudanaises de I'Afrique Occidentale française. Cet Acarien avait été rencontré par G. Bouet à, Djenné, dans des trous d'arbres ou des cases obscures servant de refuges à plusieurs espèces de chauve-souris: Hipposiderus tridens Et. Geoff., Taphozoüs perforatum Geoff., cette dernière espèce parasitée par un trypanosome.

Most of the published descriptions of R. prowazeki in lice have dealt with the minute round, oval, diplococcal or dumb-bell forms found by Ricketts and Wilder (1910), Sergent, Foley and Vialatte (1914), da Rocha-Lima (1916), and others.

Evidence exists that lethal activity is associated with extracts from Eimeria tenella-infected caecal tissues. We examined tissues of the small intestine infected with other species of Eimeria for a similar lethal activity. Extracts were prepared from intestinal tissues of chickens infected with either E. acervulina, E. brunetti, E. maxima, E. mitis or E. necatrix. Appropriate control extracts from tissues of non-infected chickens were also prepared. Intravenous injection of the extracts into healthy chickens showed that lethality of infected tissue extracts was higher than control extracts and was independent of the site of infection within the intestine. Comparison of the lethality of caecal extracts from chickens infected with embryo-adapted or parent lines of E. tenella showed that lethality was independent of the recognized pathogenic characteristics of the lines. Also, it was demonstrated that lethal activity is associated with extracts of tissues containing massive numbers of arrested and non-arrested sporozoites and early trophozoites.

In this brief note it is not my intention to enter into detailed criticism, but merely to express my surprise and that of other proto-zoologists, that the personal opinions of the Recorder should be allowed insertion in the Zoological Record (1909) which is also the International Catalogue of Zoological Scientific Literature. Against this procedure I beg to record an emphatic protest.

A robenidine-resistant strain of Eimeria maxima was found to be drug-dependent and developed satisfactorily only in birds which were receiving the drug in the diet. Normal parasite development occurred in the presence of 132 ppm of robenidine in the food.

The material used in the present study was part of a collection of parasitic worms, from whales in the Ross Sea, given to the writer by Mr W. Ross Cockrill, F.R.C.V.S. A general account of this collection has already been published (Rees, 1953).

Attempts were made to infect Stomoxys calcitrans, Lucilia sericata and Musca domestica with embryonated eggs of Toxocara canis and Toxascaris leonina. Only Musca domestica was successfully infected with Toxocara canis eggs.

Six Beagle pups were given anthelmintic treatment and infected flies were then fed to five of them. The five pups were examined at varying intervals, the sixth being used as a control. Four of the experimentally infected pups showed evidence post-mortem of having become infected with Toxocara canis by the ingestion of Musca domestica. Larvae of Toxocara canis were recovered from several tissues. Immature and adult forms were recovered from the intestinal contents. The results suggest that flies of Musca domestica are not only a source of infection to the dog, but that they may be of importance in the spread of toxocariasis in man.

I would like to thank Professor A. O. Betts and Dr W. P. Beresford-Jones for their encouragement and helpful criticism and also Mr G. Yeoman and Mr B. C. Warren of Beecham Research Laboratories, Wheathampstead, for their assistance and for the supply of flies. I am also very grateful to Mr and Mrs D. Appleton, Carmarthenshire, Wales for their co-operation in treating and supplying the beagle pups.

The chronic, recrudescent nature of malaria has been linked to antigenic diversity of the parasite in which protective immunity against Plasmodium falciparum may be obtained after repeated exposure to infection during a long time. In this study we show that parasite populations with decreased sensitivity to antibody-mediated growth inhibition are readily generated in vitro. A laboratory strain, F32, was cultured for long periods (10–12 weeks) in the presence of suboptimal inhibitory antibody concentrations. The antibodies used were the human monoclonal antibody 33G2 reacting with a linear epitope of the P. falciparum blood-stage antigen 332 and rabbit antibodies to repeat sequences of the blood-stage antigen Pf155/RESA. Our data indicate that the P. falciparum parasites adapt to antibody pressure as reflected by their specifically decreased sensitivity to growth inhibition. A relative resistance of the parasite to growth inhibition mediated by the antibodies used in the culture developed successively, while the parasite remained sensitive to growth inhibition by other antibodies. When the antibody pressure was removed a successive return of sensitivity to growth inhibition developed. Immunofluorescence did not reveal any significant difference in antigen expression between the parasite populations. However, PCR analysis showed that a new population appeared in the parasites grown in the presence of mAb 33G2, while no such change was detected in those grown in the presence of the rabbit antibodies. Our data suggest that the specific decrease in sensitivity to growth inhibition may either be due to down-regulation of antigen synthesis or expression by antibody pressure or, that antibody pressure selects for parasites with low expression of a specific antigen from a heterogeneous parasite population.