A new species, Otodistomum plunketi, is described from the Lord Plunket's Shark Scymnodon plunketi caught in Otago Harbour, New Zealand. This species is compared with Otodistomum veliporum and O. pristiophori, from which it is mainly distinguished by its size, shape, egg-size and undulating caeca.

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.

An attempt to differentiate by means of the electron microscope between particles of the top and bottom components of the turnip yellow mosaic virus is described. Since the particles of the top component are thought to be hollow spheres, it might be expected that they would collapse after drying and thus throw a smaller shadow than the particles of the bottom component which are thought to have a more solid centre. No difference could be perceived between the two types of particle, so that the apparently hollow particles can withstand the effect of drying without collapsing.

Sections were cut of leaves of Chinese cabbage (Brassica chinensis) and particles were observed inside the cells which could conceivably be virus particles.

The present paper is the third of a series dealing with a collection of parasitic worms from fishes off the coast of Iceland. The two previous papers have been concerned with the Cestoda and Digenea respectively (Rees, 1953a, b). There are no existing records of Monogenea, Nematoda or Acanthocephala from fishes off the coast of Iceland. Although this collection is not a large one, it indicates a wider geographical range of parasites already recorded from marine fishes in other parts of the world. There are five new host records.

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.

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 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.

Among a large collection of alcohol material of Danish fleas, belonging to the Universitetets Zoologiske Museum at Copenhagen and kindly sent to me for identification by Dr S. L. Tuxen, was a tube which not only contained the fleas Chaetopsylla trichosa Kohaut (6 ♂, 22 ♀) and Paraceras melis melis (Walker) (3 ♂, 30 ♀), but also a large number of the chewing louse Trichodectes melis (Fabricius). These female of Trichodectes melis, is firmly attached on the outside of the left mid-tibia by having its mandibles entirely surrounding the tibia (Fig. 1). The two insects have been mounted on one slide (which is incorporated in the British Museum collection of fleas at Tring) and the attachment of the louse to the flea is so firm that the act of preparation did not separate the two insects.

In August 1952 one of the authors captured a series of rodents of the type Rattus rattus alexandrinus at Costermansville. The rats were examined at the Medical Laboratory, Astrida (Ruanda), by kind permission of the Director, Doctor J. B. Jadin. Two species of trombiculids were found in one ear, which was very scabby and contained other microscopic arachnidians.

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.

From the Virus Research Institute, Entebbe, Uganda, the author received a number of tubes containing mites collected from small mammals in the course of yellow fever investigations. One of the tubes with mites taken from a hyrax (Procavia ahyssinica meneliki Neumann) contained two new species of larval Trombiculidae which are described in this paper under the names Schöngastia haddowi sp.n. and Eutrombicula lumsdeni n.sp. in honour of the donors, Drs A. J. Haddow and Russell M. Lumsden.

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.

Dipetalonema sprenti n.sp. is described from specimens removed from the peritoneal cavity of beavers (Castor canadensis) from Ontario, Canada. D. sprenti is found to be similar to D. arbuta Highby, 1943, but differs in the larger size of the eggs and fully developed embryos, the greater lengths of the spicules, the arrangement of the medial post-anal papillae, the more posterior position of the nerve ring, the greater length of the tail and in the considerably larger size of the body. D. sprenti is the fourth species of Dipetalonema described from rodents.

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. The description of the female and nymph of the so-called variety I. percavatus var. rothschildi is enlarged.

2. As far as the evidence is available it parasitizes marine birds and is probably a three-host tick.

3. Its systematic affinities are discussed, and since I. percavatus is synonymous with I. auritulus, then the variety of Nuttall & Warburton should be raised to the specific rank of I. rothschildi.

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.

On the available data from south Wales and southeast England, the tick Ixodes hexagonus Leach has spring and autumn peaks of activity on hedgehogs, stoats and weasels.

One or more stages of this tick have been recorded on fifteen mammalian hosts. All stages have been collected from hedgehogs, stoats, foxes, polecats and ferrets. The weasel is probably the smallest habitual host. No specimens of I. hexagonus have been found on birds.

Man is an ‘accidental’ host and records of this tick on man in the London area are given. From the present information it seems that ill-effects following the bite of this parasite are rare. In built-up areas the probable sources of infestation are dogs, cats and hedgehogs. Air-raid shelters and similar constructions which have harboured these hosts at one time or another may provide a centre of infestation of man. Our observations indicate that the number of ticks in most hedgehogs' nests is not large. Nothing is known of the tick population in the habitats of other hosts. It is suggested tentatively that the ticks may drop off hedgehogs away from the nest and that after further development (i.e. hatching of eggs and metamorphoses of later stages) they are picked up by such animals as foxes, stoats, weasels.

The records of this tick in Britain are summarized and they indicate that I. hexagonus is a southern species.