The genus Ischnopsyllus Westwood, comprising at the moment sixteen species and subspecies, is rather a heterogenous group. Although I am reluctant to split this relatively small genus, a certain degree of division is unavoidable. First, I. grahami Waterston certainly does not belong to the genus Ischnopsyllus, and since this species does not fit any other genus of bat-fleas, a new genus has had to be erected for it (see below, where a new subspecies of grahami is also described). Secondly, the hexactenus-group of Ischnopsyllus is sufficiently distinct from the rest of the genus to make it desirable to restore, as a subgenus, the genus Hexactenopsylla Oudemans, which was synonymized with Ischnopsyllus by Dalla Torre in 1924.

The genus Petasiger which belongs to the family Echinostomidae was proposed by Dietz in 1909, with Petasiger exaeretus as the type species. The description given by Dietz of this species is incomplete and it is proposed therefore to present below a more detailed account of the anatomy, based on an examination of whole mounts and serial sections. The material was obtained from the small intestine of cormorants shot on the coast of Cardigan Bay between Aberystwyth and Llanrhystyd. Five cormorants were shot in July, and of these two contained a large number of Petasiger exaeretus in the small intestine.

The following is a description of a new species of Accacoeliid Trematode found in the intestine of a sun-fish (Orthagoriscus mola Bloch), caught by a fisherman in June, 1933, at Salcombe, Devon. The fish was examined by Mr J. W. Poulton of Downing College, Cambridge, to whom my thanks are due for bringing me the parasites for identification. In addition to the species described in this paper the host contained the following forms: on the skin, Tristoma molae and Lepeophtheirus nordmanni; in the intestine, Ancistrocephalus microcephalus.

The distribution of two stages of the nematode Labiostrongylus longispicularis (Wood) in thirty-eight stomachs of the Red Kangaroo, Megaleia rufa (Desmarest) has been analysed statistically.

A quadratic regression was used where y = log of mean worm densities of stomach sections + 1 and x = numerical values of the mid-positions of the sections. The analysis revealed significant maxima in the proximity of the cardiac region. The maxima in stomachs with relatively large numbers of worms were found to be further away from the pylorus than in the stomachs with small numbers of worms. The mean maximum densities were about fifty worms per 100 g of stomach content in highly infected animals and about eight in low infections. It is suggested that freshly chewed food or saliva may be a factor regulating the distribution of worms.

The parasite was absent from the stomach's pyloric region where the pH is low.

Sex and size of the worm were independent of its position in the stomach.

The average number of eggs per adult female in the different stomach sections roughly corresponded to the density of worms in these sections, but the sample material was inadequate to show that this relationship was statistically significant.

The mean number of fertilized eggs per female worm was 3300.

Thanks are due to Professor E. J. Williams of the University of Melbourne and Mr B. V. Fennessy of the Division of Wildlife Research, C.S.I.R.O., for reading and criticizing the manuscript, and to Messrs E. R. Hesterman and C. Kogon for technical assistance.

The multi-host lifestyle of parasitic trematodes necessitates their ability to communicate with their external environment in order to invade and navigate within their hosts' internal environment. Through recent EST and genome sequencing efforts, it has become clear that members of the Trematoda possess many of the elaborate signal transduction systems that have been delineated in other invertebrate model systems like Drosophila melanogaster and Caenorhabditis elegans. Gene homologues representing several well-described signal receptor families including receptor tyrosine kinases, receptor serine tyrosine kinases, G protein-coupled receptors and elements of their downstream signalling systems have been identified in larval trematodes. A majority of this work has focused on the blood flukes, Schistosoma spp. and therefore represents a narrow sampling of the diverse digenean helminth taxon. Despite this fact and given the substantial evidence supporting the existence of such signalling systems, the question then becomes, how are these systems employed by larval trematodes to aid them in interpreting signals received from their immediate environment to initiate appropriate responses in cells and tissues comprising the developing parasite stages? High-throughput, genome-wide analysis tools now allow us to begin to functionally characterize genes differentially expressed throughout the development of trematode larvae. Investigation of the systems used by these parasites to receive and transduce external signals may facilitate the creation of technologies for achieving control of intramolluscan schistosome infections and also continue to yield valuable insights into the basic mechanisms regulating motility and behaviour in this important group of helminths.

We believe that the publication of a new key to the species of the genus Polyplax, so soon after that contained in Ferris's recent monograph (Ferris, 1951), is justified since it includes two new species and three species, praomydis Bedford, subtaterae Bedford and cummingsi Ferris, which appear to require some re-definition as Ferris placed all three in synonymy.

The experiments with warble-fly larvae, taken in conjunction with the evidence of Carpenter and Gläser, lend support to the view that they gain an entrance through the skin.

The hypothesis is advanced that the larvae select the gullet for reasons connected with their development and growth. These may be: a freer supply of oxygen, and a loose areolar tissue which offers comparatively little resistance to them.

The position of the larva under the hide is horizontal. In this position the skin movements affect it but slightly, or less than if the position were perpendicular.

H. lineatum does not terrify cattle as does H. bovis, the fly was seen ovipositing and the animals showed little uneasiness during the process.

The seasonal activity of H. lineatum is earlier than that of H. bovis.

Observations were made on oviposition which confirmed those of Riley and Gläser.

Two experiments were tried with larvae, to see if they would penetrate the hide, but no definite results were obtained.

Further proof is afforded of the terror which H. bovis inspires in cattle. It was observed that animals, exhausted by running, occasionally lay down and became more or less indifferent to the attacks of the fly. On these occasions the eggs were laid higher up on the host's body.

1. Two pure strains of Entamoeba coli, differing in their accompanying bacterial flora and experimental history, but identical morphologically, have been tested with emetine hydrochloride in vitro.

2. In a buffered and wholly liquid medium, with a pH varying between 6·8 and 7·2, emetine hydrochloride was found to be toxic to E. coli in dilutions between 1 : 300,000 and 1 : 600,000, the toxicity increasing with the alkalinity of the medium.

3. It is therefore concluded that emetine is about 16 times as toxic in vitro to E. histolytica as it is to E. coli.

Mongolian jirds, Meriones unguiculatus, are susceptible to infection with Trypanosoma grosi, which naturally parasitizes Apodemus spp. The present study investigated T cell dependence of elimination of T. grosi from the bloodstream of jirds by in vivo T cell depletion using a monoclonal antibody (HUSM-M.g.15). In T cell-depleted jirds, elimination of T. grosi, particularly the dividing forms, from the bloodstream was significantly delayed, occurring at around week 3 p.i. The kinetics of serum levels of IgM and IgG specific to trypanosomes in T cell-depleted and control immunocompetent jirds were different; peak levels of IgM were noted on days 6–8 p.i. around the time of peak parasitaemia (day 6 p.i.) in immunocompetent jirds, whereas the serum levels began to increase abruptly after day 10 p.i., peaking at around day 18 p.i. in T cell-depleted jirds. Similarly, serum IgG increased after day 6 p.i. in immunocompetent jirds, in contrast to after day 12 p.i. in T cell-depleted jirds, and the level increased steadily even after disappearance of parasitaemia. Our findings indicate that T cells play a major role at least in the ‘first crisis’ during elimination of dividing T. grosi from the bloodstream.

When neonatal rats were exposed to a small (200 larvae) primary infection of Nippostrongylus brasiliensis the worms that became established in the intestine were found in the mid-jejunum on both the seventh and the fourteenth day after infection. By day 21 most of the worms had migrated to the duodenum where they remained subsequently.

When similar rats were exposed to a heavy primary infection (1500 larvae) the worms were found to be distributed along the length of the duodenum and jejunum by the seventh day. By day 28, however, a proportion of worms equal to that formerly located in the jejunum had been expelled, leaving a population of about 300 worms in the duodenum.

It is suggested that the increased longevity of those worms that survive the effects of host immunity is dependent on their location at the duodenal site. The possibility is raised that the duodenum may be an immunologically privileged site for N. brasiliensis in young rats.

Owing to the courtesy of Docent W. Stefanski, University of Warsaw, I have had the opportunity of studying some Nematoda collected by him from the large intestine of an elephant which died hi the Warsaw Circus.

The case described in this note is believed to be unique, for no similar record has been found after search of the relevant literature. The subject of myiasis has been carefully reviewed and abstracted by Huber (1899), Umaña (1915) and Bedford (1927), and no cogent references of more recent date have been discovered.

A short description is given of an important disease of sheep (Scrapie, Traber-krankheit, La Tremblante), believed to be caused by a heavy infection with Sarcocystis tenella, probably of increased virulence.

The itchiness and paresis, the congenital transmission by the mother, the non-contagiousness, the long incubation period, etc., are readily explained on this view and a method of control of the disease based on this theory has been highly successful.

The sarcocyst has been shown to be transmitted from sheep to sheep by intrauterine infection and by means of the milk.

The minute structure of the sarcocyst is described and it has been shown in particular that the sickle-shaped spores are surrounded by a capsule. Under certain conditions, as in 1 per cent, glucose water and in the centre of the ripe cyst, these spores swell out and become globular, eventually bursting and scattering small chromatin granules. The further evolution of these granules is dealt with.

The spread by means of milk and by the intestinal route is discussed1.

In a previous paper (1931) the writer described the presence of a spicule in the male of Capillaria [Hepaticola] hepatica, and gave reasons for believing that the apparent presence or absence of a spicule in the males of forms closely related to it is not a reliable taxonomic character. It was suggested that the genus Eucoleus Dujardin, which, like Hepaticola Hall, was based mainly on the supposed absence of a spicule, should likewise be suppressed as a synonym of Capillaria. Teixeira de Freitas & Lent (1935, 1936), in accepting this view, have drawn attention to an observation recorded by Creplin (1849), which had been generally overlooked, to the effect that a spicule is present in the genotype of Eucoleus (Trichosomum aërophilum Crepl., in Ersch & Gruber, 1839). Up to the present Creplin's observation has not, so far as the writer is aware, been confirmed. Some specimens of Capillaria aërophila from the lungs of silver foxes were recently received from Mr C. V. Watkins, M.R.C.V.S., who had noticed in a living male specimen what appeared to be a spicule projecting from the everted spicule-sheath, and enclosed a sketch of it in his letter. On examining the preserved material, the writer was able to confirm this interesting observation. In the specimen referred to by Mr Watkins, and in another individual, a very delicate structure, apparently a spicule, was seen projecting for a short distance beyond the end of the partly everted sheath.

In order to visualize low-pH compartments of Plasmodium berghei strains we have used a basic congener of dinitrophenol, 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine (DAMP) which concentrates in acidic compartments, and can be detected by immunocytochemistry with anti-dinitrophenol antibodies. We have demonstrated that in a P. berghei chloroquine-sensitive strain (N strain), DAMP accumulates in the endocytic vacuoles where haemoglobin degradation is occurring. These compartments which have recently been shown to concentrate 4-aminoquinoline drugs (Moreau, Prensier, Maalla & Fortier, 1986) have an acidic pH. Conversely DAMP was found scattered all over the cytoplasm in a P. berghei chloroquine-resistant strain; the same phenomenon was previously observed (Moreau et al. 1986) in the localization of a 4-aminoquinoline on this same strain. Monensin-induced swelling of acidic compartments (Boss & Morre, 1984) was used as a complementary method for the determination of low-pH compartments on P. berghei strains. All the data reported here suggest that chloroquine resistance in P. berghei RC may be related to an impairment in the acidification of endocytic vesicles.

This species has received so few notices from collectors of parasitic Copepoda that it might be judged uncommon. Thus Krøyer (1837), originally placed it in the genus Lernaeopoda having but a single specimen at his disposal the host of which he had forgotten; subsequently it has been recorded by Olsson (1869), who was the first to place it correctly in the genus Brachiella. This species has also been recorded by P. J. van Beneden (1870), by T. Scott (1901), by A. Scott (1904), and collected by L. Harrison Matthews, as mentioned by me (1926), at Plymouth.