Full development of Oswaldofilaria chlamydosauri (Breinl) was obtained in Culex fatigans Wied. and Culex annulirostris Skuse. Infections in four lizards were observed 4–6 months after inoculation of infective larvae from both species of mosquitoes.

In August 1948 a student from this department, Mr J. N. Upton, went on a commercial trawler to the fishing grounds off the coast of Iceland and brought back a collection of parasitic worms from some of the fishes caught in the trawl. Being unable to continue the investigation Mr Upton handed the specimens to the writer for identification and further study. The writer is most grateful for the gift of this collection.

1. Eight species of digenetic trematodes, including one new species, have been recorded from six species of host fishes caught in the trawl off the east coast of Iceland.

2. Seven species are recorded for the first time from this locality and there are two new host records among the seven known species.

3. Details of the exact locality and depth from which the fishes were taken are given, together with a brief account of each known trematode and a more extensive account of the new species, Steganoderma pycnorganum.

The material examined in the present investigation was given to the writer by Mr W. Ross Cockrill, F.R.C.V.S., Veterinary Officer, Ministry of Agriculture and Fisheries, Carmarthen. The specimens were collected by Mr Ross Cockrill on the whale factory ship Balaena when he accompanied the Antarctic Whaling Expedition in the winter of 1951–2 for the purpose of making investigations into the pathology of whales. The whales were caught in the Ross Sea area roughly between 67° 51′ S. and 71° 13′ S., and the parasitic worms recovered from them include cestodes, nematodes and Acanthocephala. The worms were fixed at the time of collecting, the cestodes in 5% formalin and the nematodes and Acanthocephala in hot 70% alcohol. When only one or a few specimens were found they were all fixed, but if the infestation was heavy a sample was collected. In addition, portions of infested kidney and lesions from other parts of the body thought to be associated with parasitic infestation were included in the collection. The writer is greatly indebted to Mr Ross Cockrill for the gift of this material.

The longevity of laboratory-reared fleas, two species parasitic on domestic rats and six species parasitic on wild rodents of the sylvatic plague reservoir, was studied. The 10,795 adult fleas used in these studies were maintained at different temperatures and humidities within a range encountered in their natural habitats. Different conditions of host availability were simulated by feeding some adult fleas only once, at the beginning of an experiment, by feeding others daily, and by not feeding others at all.

Generally, a single blood meal exerted a beneficial effect on the fleas in that those fed before starvation survived a little longer than those that were never fed.

With the exception of Opisodasys nesiotus, all fleas were potentially long-lived under some of the laboratory conditions. The longest-lived fleas in all instances were those kept at high humidities (90% relative humidity or more) and fed daily. An O. nesiotus male survived for 48 days, the longest period of any of this species. The maximum longevity for each of the other species was among females and was as follows: Xenopsylla cheopis, over 5 months; Malaraeus telchinum, over 6 months; Nosopsyllus fasciatus, over 9 months; Orchopeas sexdentatus sexdentatus, 10½ months; Diamanus montanus, over 11 months; Oropsylla idahoensis, nearly 12 months; Megahothris abantis, nearly 16 months.

In the last 30 years, at various laboratories in the United States, France and England, many strains of small holotrichous ciliates have been established in axenic culture for use in a widening variety of investigations of a physiological or biochemical nature. Since few of these organisms have been adequately described or properly identified by the workers employing them, thus making difficult meaningful comparison of the various experimental results reported, the need for morphological and taxonomical study has become increasingly apparent. At least twenty-nine such axenic strains of ciliates, considered members of a ‘Colpidium-Glaucoma-Leucophrys-Tetrahymena group’ because it has been principally to these four genera that the protozoa have been assigned in the past, are still in existence and twenty-six of them were collected for use in the present investigation. For accurate identification of such relatively undifferentiated ciliates the use of silver nitrate impregnation techniques, the value of which was recognized some years ago by Klein (1926) and stressed by Furgason (1940), is re-emphasized as being nearly indispensable. Details of buccal organelles and differentiated pellicular structures in other parts of the body are revealed precisely and with constancy.

1. The shell gland of Fasciola hepatica produces an extremely hyaline secretion. The egg-shell is formed from the hyaline secretion.

2. As the eggs travel through the uterus, the shell is temporarily reinforced from the inside by vitelline granules. The vitelline granules are released when the vitelline cells enter the vitelline reservoir.

3. Views regarding the nomenclature of the shell gland are discussed.

4. The presence of an elliptical chamber in the shell gland is described. In this chamber, oocytes, vitelline granules and vitelline cells are mixed together, and here the secretion of the shell gland is released and the egg-shell is formed.

5. The arrangement of the cellular constituents within the egg is effected by the elliptical chamber.

1. The nematode Rhabditis pellio Bütschli may be cultured indefinitely on earthworm extract.

2. Although the females of this nematode are usually capable of parthenogenetic reproduction, males are produced in the offspring only if copulation has taken place.

3. Occasionally non-parthenogenetic generations appear but these do not represent a separate species.

4. An explanation is given for the sex ratio found under natural conditions and it is suggested that sex-determination works on a chromosomal arrangement of XO = male and XX = female.

5. The nematode named R. terrestris Stephenson 1942 is probably the same as that named R. pellio Bütschli by Johnson 1913.

6. The nomenclature of R. pellio Bütschli is discussed.

An investigation of the occurrence of helminthic intestinal parasites in the population of central and southern Iraq led to the discovery that human trichostrongylosis is relatively common in man along the banks of the Shatt-al-Arab and the lower course of the Tigris and Euphrates rivers. In the Basrah area the incidence is 25·4% and at Nasriyah 14·2% but it falls rapidly along the northward course of the rivers and is absent in the centre and north of the country. This is correlated with the occurrence of heavy shade cast by palm forest, high humidity due to the presence of perennial swamps, and the occurrence of grass and other carpet plants in the south; which jointly provide the conditions necessary for the development and survival of the free-living stages of Trichostrongylus.

Hookworm (Ancylostoma duodenale) is more evenly distributed over the area and is common farther north where conditions are more arid; owing to the fact that the free-living stages can develop under much drier conditions than those of Trichostrongylus, probably mainly on moist defaecation sites near irrigation channels.

The species of Trichostrongylus involved is not known but is probably T. colubriformis which is common locally in sheep and has been found in man at Abadan by Marsh (1949). Infection is presumably contracted by ingestion of greenstuff carrying infective juveniles.

Since infections are light, symptoms minimal and treatment ineffective care should be taken to differentiate trichostrongylosis from ancylostomiasis in order that no unnecessary medication be undertaken.

The world incidence of human trichostrongylosis is higher than was formerly believed. The available reports are reviewed, and it is concluded that not less than fifty million persons harbour this worm throughout the globe.

1. Experiments were carried out with the object of devising means of maintaining large numbers of Glossina in the laboratory, especially for experimental work in trypanosomiasis.

2. Most of the experiments were done with the local species, G. swynnertoni, but maintenance of G. morsitans, G. pallidipes and G. austeni was also attempted.

3. Maintenance at a constant temperature of 26° C. was a complete failure, chiefly owing to the impossibility of maintaining an adequate humidity with the apparatus used.

4. Maintenance in the laboratory (with higher temperatures and consequently lower r.h. for most of the twenty-four hours) gave very poor results and inadequate length of life.

5. Longevity of flies was much improved by keeping them in an open-sided thatched hut in cages over water, and mean lives of up to 110 days in a cage of ten flies were achieved—even over the most severe part of the dry season.

6. Flies were fed in one of two ways: on guinea-pigs in a ‘Geigy’ feeding-rack or on sheep in a crush by fixing the cages round the flanks and abdomen of the sheep with an elastic band.

7. Earlier comparisons of the two methods of feeding either were inconclusive or favoured guinea-pig feeding. After prolonged maintenance the G. swynnertoni fed on sheep gave much the better results. G. pallidipes, from the beginning of maintenance, did much better on sheep-feeding.

8. The population of G. swynnertoni fed on sheep has increased progressively up to the sixth and seventh laboratory-bred generation; the guinea-pig-fed population showed an early increase but has since declined sharply.

9. Fertilization of females in the laboratory has been easily achieved with G. swynnertoni and G. austeni. G. morsitans has shown some failures, and with G. pallidipes great difficulty was encountered.

10. Records of pupal weights and weight-loss have been kept and methods of keeping pupae studied.

11. Results indicated that total weight-loss of pupae was dependent chiefly on humidity and but little, if at all, on temperature; the pupae were therefore finally kept at laboratory temperatures at constant 90% r.h.

12. In early generations of G. swynnertoni and G. morsitans there was significant negative skewness of the distribution curves of initial weights of pupae, indicating an excess of small or ‘runt’ pupae. Flies emerging from these under-weight pupae were eliminated from the maintained population; the lower limits of initial pupal weight, below which the emergent flies were excluded, were 22 mg. for G. swynnertoni and 24 mg. for G. morsitans.

13. In general, there has been a decrease in the mean weight of pupae from generation to generation, except that the course of the decrease has been very different in the two differently fed populations. In the guinea-pig-fed population weights were high in the early generations and later dropped sharply; in the sheep-fed population weights were rather lower at first but have decreased only slightly and then, in the latest generations, increased a little.

14. There has been an increase in the total weight-loss of pupae from pupation to emergence in later generations.

15. The mean interlarval period has been consistently longer than the known period for Glossina at the temperatures experienced, indicating a proportion of abortions up to as much as 50%.

16. Total weight-loss of pupae was found not to be a constant amount as has been stated elsewhere but to be in proportion to pupal size.

17. A consistent sex-difference in total pupal weight-loss was found in the pupae of G. swynnertoni examined, the males losing 1·1–1·6% more of their initial weight. Data are given to show that this difference is fully established within the early period of rapid weight-loss and only increased a little by the greater loss in the males in the last few days before emergence.

18. The early results of maintenance of G. austeni have shown remarkable longevity and very good reproduction-rate, both exceeding the records of other species maintained.

19. It is suggested that G. austeni may prove to be a valuable laboratory vector of trypanosomes in view of these promising results in a climate very different from that of its natural habitat.

The life history of Ornithodoros graingeri under laboratory conditions at 28° C. and 95% humidity, can be summarized as shown in Table 4. These figures, except for the fourth-stage nymphs, include the interval between emergence and willingness to feed.

A spirochaete, S. graingeri n.sp., was isolated from batches of Ornithodoros graingeri from caves near Tiwi, south of Mombasa. Very scanty infections were caused in white rats and mice, and a persistent parasitaemia in a general paralytic. Guinea-pigs, a monkey, and a young rabbit were insusceptible. There was evidence that unlike most tick-borne strains the spirochaete was only slightly neurotropic.

The purpose of this paper is to describe a new tick of the genus Ornithodoros Koch, from South Africa. Specimens were received through the courtesy of Dr Zumpt of the South African Institute of Medical Research, after being collected from the burrow of a striped mouse, Rhabdomys pumilio (Sparrman), near Cathcart, Cape Province, in April 1952. Interest in the ‘burrow haunting’ Ornithodoros of Africa has increased in recent years, because certain of these ticks have been found to transmit spirochaetes of rodents and other small mammals. These spirochaetes may be evolutionary precursors of those that infect man, and cause the well-known sporadic relapsing fever of tropical Africa. Two live Ornithodoros larvae from the burrow were emulsified and inoculated into a white mouse but no spirochaete was isolated (Zumpt, personal communication).

For the purpose of determining the suitability of malaria for some work on experimental epidemiology, it was necessary to study the reciprocal immunity produced between a number of species and strains of avian plasmodia maintained in canaries. Some of this work has been a repetition of that previously described by other authors, but some new observations have been made, involving a number of geographically widely separated species and strains, which seem worth putting on record.

Among approximately eighty larvae of Trachea secalis, gathered from the same locality near Cape Town, South Africa, the incidence of microsporidian infection has been found to be 100%. In the majority of cases the parasite had heavily involved the lower portion of the gut, whereas the rectum and the upper portion of the gut were never infected. In severe cases the gut tissue was practically destroyed and replaced by an almost solid mass of spores. Except during the stages preceding spore formation, the infected portion of tissue can be detected by the unaided eye. When spores have been produced in large numbers, the involved area, which may be no larger than the head of a pin, and is usually located within the posterior third of the gut, becomes white and opaque, and contrasts sharply with the healthy surrounding tissue. The latter is transparent, and appears dark, owing to the colour of the contents. At a later stage it is not unusual to find the infected zone in the form of a narrow band which encircles the gut. The infection then spreads upwards and downwards. Finally, the entire lower portion of the gut becomes white and chalky. With the exception of the gut contents the parasite has not been found elsewhere in the body of the host.

At one of the meetings of the Royal Society of Tropical Medicine and Hygiene, I made a very short communication on the three blood-sucking midges (Jobling, 1929). My particular reference was to Culicoides vexans, which is the most troublesome and commonestspecies in spring, in the northern and the north-western suburbs of London. At that time I had been studying the life history of this midge, including the morphology of its eggs, larvae and the pupa, but this work was not completed.

1. A description is given of a sporozoan parasite occurring in the coelomic fluid of P. minutum.

2. The four stages described include two types of schizonts (each enclosed in a tough envelope), merozoites, trophozoites, and encysted gamonts. The schizonts occur in the haematids of the coelomic fluid, the ‘cysts’ in amoebocytes.

3. The life history and possible affinity of the parasite with the Haemogregarinidea are discussed.

4. Attempts to verify the suggested life history by experimental means are described.

In tests for chemotherapeutic activity, mice were infected with Eperythrozoon coccoides, treated with drugs for 2 days, splenectomized, and treated with drugs for a further 2 days. Blood films were examined from the second day after splenectomy, when control mice showed heavy blood infections.

Neoarsphenamine, aureomycin and terramycin were active.

Tryparsamide, Chloromycetin, alloxan and polyoxyethylene ether, D2, were slightly active.

Many drugs, listed in Table 3, were inactive.

Neoarsphenamine cleared E. coccoides from the blood very rapidly. This action was inhibited by dimercaprol (BAL).

E. coccoides closely resembles Haemobartonella muris in its sensitivity to drugs. Both micro-organisms probably have affinities with the Rickettsiae.

When reviewing the status of Ixodes frontalis Panzer in an earlier paper (Arthur, 1952) the reference to Acarus (Ixodes) turdi Scopoli was not included, for the description might well apply to any tick. This is equally true for Panzer's description, and this name has been retained through popular usage. Neumann (1899) was the first worker to present a fairly clear account of this species but, as his host range shows, it may well have been clouded by reference to Ixodes brunneus Koch. The available descriptions refer to the female. Larvae have hitherto been neglected or else described as similar to the female, with the addendum that ‘in the larva the scutum is as broad as long’. Examination of ticks from a large number of birds has convinced me that in the past the immature stages of many species of ticks have, on this basis, been incorrectly determined. This may possibly be one reason for the suggested rarity of records of the immature stages of I. frontalis. In the present paper the larva of this species has been described. This description has been based on larvae sent to me by Mr John Ash.

Up to the present time the polyhedral viruses of insects have been considered to be extremely specific in their infectivity, and cases of cross-infection, even between closely related species, were regarded as rare occurrences. Recently, however, we have recorded results which suggest that there is no such specificity of infection (Smith & Xeros, 1952). In the following paper we describe the results obtained in an extensive series of cross-inoculations among a heterogeneous collection of lepidopterous larvae, selected entirely at random. The results obtained appear at first sight to be compatible with one clear-cut explanation of straightforward cross-infections with differential multiplication of two different viruses in different hosts. Other complications, however, cannot be excluded and one or two possible situations are discussed later in the paper.