In a collection of the early stages of Simuliidae, made by Mr F. W. Edwards, in the summer of 1923, from the rapids above Tännforsen waterfalls, Sweden, there are representatives of 11 species of Simulium: larvae and pupae of S. venustum Say and S. tredecimatum Edw., larvae of S. morsitans Edw. and S. reptans var. galeratum Edw., pupae of S. tuberosum Lundstr., larvae and pupae of S. pusillum and pupae of S. pallipes Fries and S. lyra Lundstr., besides pupae of three other indeterminable species. In a previous paper I have already described, in detail, the early stages of the first five species, and in the present paper I deal for the first time with the remaining six species and the early stages of S.ferruginum Wahlgr. The pupae of S. pusillum Fries, S. pallipes and S. lyra were identified by Mr Edwards, by dissecting out the male genitalia, but those of the remaining three species, herein described as species I–III, are indeterminable owing to their immaturity. It seems inadvisable to give the pupae new specific names as further investigation may prove that they belong to well-known Continental species.

In the paper on the association of Rickettsia with Trench Fever, by Arkwright, Bacot and Duncan (1919) mention is made of a bacillary infection of the excreta and guts of lice (Pediculus humcmus). A Gram-negative cocco-bacillus was isolated in pure culture. It was non-motile, fermented glucose, mannite and lactose very slowly, and formed acid and clot in milk in about 14 days.

The inheritance of an antigen designated Py-1 in the rodent malaria parasite Plasmodium yoelii has been investigated. A cross was made between 2 lines differing in the electrophoretic mobility and quantity of Py-1 detected by crossed immunoelectrophoresis. In 10 clones isolated from the progeny of the cross the level of Py-1 always correlated with the virulence of the infection and it was concluded that these characters were different phenotypic effects of the same gene mutation. The electrophoretic mobility of Py-1 segregated independently of the virulence character and was therefore controlled by a different gene. These two antigenic markers also recombined with isoenzyme and drug-sensitivity characters distinguishing the parent lines.

Uric acid is the most important constituent in the urine of insects. Infective metacyclic forms of the stercorarian trypanosomes are produced in the rectum of their insect vector and are thus in contact with uric acid. Using a culture system which permitted the growth of the insect stages of Trypanosoma musculi, we studied the influence of uric acid on the metacyclogenesis of this parasite. When added to the culture, uric acid enhanced the production of metacyclic forms. Furthermore, it rendered these trypanosomes highly infective by the oral route. It is suggested that uric acid may play an important role on the metacyclogenesis of T. musculi.

The fluorescent probe 1-anilino-8-naphthalene suiphonic acid (ANS) was used to investigate the effect of temperature on the physical state of the mitochondrial membranes of adult and larval schistocephalus solzdus together with that of their hosts Gasterosteus aculeatus and Gallus domesticus. Arrhenius plots of ANS/membrane fluorescence for S. solidus plerocercoids was linear over the temperature range 15 to 58 °C, while that for the adult was biphasic with a discontinuity at 39·9 °C. This was interpreted as a physical change which occurred in the adult membrane but not in the plerocercoid membrane and pointed to an alteration in membrane composition during infection. Gasierosteus aculeatus showed a linear Arrhenius plot for membrane fluorescence, irrespective of acclimation temperature. Gallus domesticus showed a discontinuity in the Arrhenius plot for membrane fluorescence at 46·9 °C, outside the normal physiological temperature range.

Possible relationships between the numbers and development and growth of Haemonchus contortus and Nematodirus battus during concurrent infections and the levels of abomasal pH and Na+ were investigated in 2- to 3-month-old and 8-month-old lambs. The percentage of Haemonchus in the fourth larval stage was found to be positively related to the levels of abomasal electrolytes, while the mean lengths of the worms in the total male and female populations and in the fifth-stage populations were negatively related to these parameters. The numbers of Nematodirus and the mean lengths of worms in the total and fifth-stage populations were negatively related and the percentage of worms in the fourth-stage positively related to abomasal pH and Na+ levels. It is suggested that the changes in abomasal physiology caused by massive infections of Haemonchus directly affect the growth and development of this abomasal parasite. It is also suggested that the changes in the abomasal contents entering the proximal part of the small intestine during such infections of Haemonchus alter the intestinal environment and that this alteration directly affects the course of development of concurrent infections of Nematodirus.

André & Colas-Belcour (1942) described the male of Ixodes kerguelenensis as a variety of I. canisuga on the basis of one specimen. Subsequently Zumpt (1952) stated that its status as a full species was unquestionable, for, compared with I. canisuga, the jugular plates on each side of the pregenital plate in I. kerguelenensis are large. The structure of Haller's organ also fully justifies this separation (Arthur, 1956). Zumpt wrote further that: ‘The specimen on which the authors based kerguelenensis was probably fully engorged so that the ventral plates would be widely separated from each other…. The single male from Kerguelen is drawn as having the anal groove diverging, but this is certainly due to a distortion of the engorged tick.’ Through the courtesy of Professor André I was permitted to examine the type. Distortion is not due to engorgement, as Zumpt suggests, but to the mounting of the specimen on a slide under a cover-glass.

When specimens of the turtle, Trionyx gangeticus, and of the fish, Wallago attu, were purchased in a local market and examined, nematodes were found in the intestines of both these hosts. Two males were found in the intestine of the turtle, and a male and three females in the intestine of the fish. Examination of these nematodes showed that they all belonged to the genus Dichelyne Jägerskiöld, 1902, but that none of them belonged to any known species of this genus. The genus Dichelyne was regarded by Yorke & Maplestone (1926) as being synonymous with the genus Cucullanus, O. F. Mueller, 1777, but was later re-instated as a distinct genus by J. F. Mueller (1934), who reduced the genus Dacnitoides Ward & Magath, 1916, to synonymy with Dichelyne. In the light of these emendations the genus Dichelyne now includes the following species: D. fossor Jägerskiöld, 1902, 1909; D. cotylophora (Ward & Magath, 1916), J. F. Mueller, 1934; D. robusta Van Cleave & Mueller, 1932; D. fastigatus Chandler, 1937; and D. diplocaecum Chandler, 1937.

Confocal scanning laser microscopy has been used to study the distribution of antigens expressed by the liver stages of Plasmodium berghei in cultured hepatoma cells. The 3-dimensional images obtained of intact parasites clearly show complex patterns of antigen expression not apparent when using conventional IFAT or immunoelectron microscopy. A liver-stage specific antigen (Pbl 1) was shown to be confined to the parasitophorous vacuole; the vacuole has extensive diverticulae extending into the host cell. Small parasites were detected for the first time in ‘mature’ cultures. These did not represent a distinct population, but the ‘tail’ of a broad continuum of parasite sizes. Irradiated sporozoites produce a transient population of slow-growing parasites which express a very limited range of antigens de novo in the invaded hepatoma cell. A comparison of the reactivity of text-abstract EE parasites with anti-circumsporozoite antibody and with anti-Pbl 1 suggests that the former reagent may reliably be used to identify sporozoites invading host cells, but should not be used to determine the number of parasites that successfully undergo intrahepatic development. Anti-Pbl-1 indicates on 33% of invaded sporozoites identified by anti-CSP subsequently differentiate.

Large numbers of Plagiorchis (M.) megalorchis Rees, 1952, were found in the small intestine of dying pheasant chicks in Peeblesshire, Scotland. This is the first record of this trematode in pheasants. In one chick one specimen of Brachylaemus fuscatus (Rud, 1819) was found, which is a new host record in this country. Unusual virulence of these trematodes in pheasants and turkeys is noted, showing lack of adaptation to these hosts. In addition to chironomids and midge, culicine larvae were infected with cercariae from naturally infected Lymnaea pereger. It is proposed to consider P. laricola Skrjabin as described and illustrated by Chertkova (1953) to be Plagiorchis bikhovskayae n.nom.

The author wishes to express his thanks to R. H. Duff, M.R.C.V.S., of the Ministry of Agriculture, Veterinary Laboratory, Lasswade, for placing the first pheasant chicks at his disposal, and to A. Howe, the gamekeeper at Holylee, for his information and willing help.

1. A detailed description, with illustrations, is given, of the sequences in development and maturation of the genitalia in Tetrabothrius erostris. This is the first such account of any member of the new order Tetrabothridea.

2. The effect of the very marked protandry on the form of the remainder of the genitalia is discussed.

3. Attention is drawn to the unusual ovary which produces sclerotin and which it is proposed to call a ‘calycal-ovarium’.

4. Comparison is made of the embryophore with that of the Cyclophyllidea. There is a suggestion that the embryophore may be formed of sclerotin in T. erostris.

5. Par-uterine vesicles have been described for the first time in any member of the Tetrabothridea. These vesicles arise from the uterine primordium and have previously been confused with testes.

6. The complex affinities of the order Tetrabothridea are discussed and some support arises for the creation of this new order.

The original description of Ixodes tatei was given by Arthur (1959) and based on three females taken from a rock partridge of unknown species and from a fox (Vulpes sp. ?) in Jarmo, Chemchemal Valley, Kirkuk (type locality) and the Zagros Mountains, Erbil, both in north-eastern Iraq. The material, on which the following account is based, consisted of two females, one gorged nymph, one slightly fed nymph and two fully gorged larvae. They were collected from the head of Alectoris graeca, which was shot about 20 km south of Jerusalem on 17 December 1966 and sent to me by Professor O. Theodor of the Hebrew University. One female, one nymph and one larva have been deposited in the Hebrew University, Hadassah Medical School, and one female, one nymph and one larva are retained in my collection. The holotype female is deposited in the Chicago Natural History Museum, Cat. no. 84472.

The tentacular bulb of Grillotia erinaceus metacestodes consists of obliquely striated muscle fibres with obvious motor end-plates. In this study isometric tension recordings and intracellular microelectrodes have been used to record mechanical and electrical activity from single isolated bulbs. Bulbs were mechanically quiescent and displayed resting membrane polentials (RMP) in the region of −49 to −64 mV with a mean RMP of −56 mV (n = 60). The membrane potential varied with [K+]o in a manner consistent with the RMP being determined largely by the K+ equilibrium potential. High K+ solution (> 15 mM) caused membrane depolarization and contraction of the preparation with the contraction showing both phasic and tonic components. L-glutamate caused membrane depolarization, contraction of quiescent preparations and increased the amplitude of electrically evoked responses. In contrast, 5-HT, dopamine, histamine, adrenaline, GABA, noradrenaline and D-glutamate, at concentrations up to and including 10−3 M, were without apparent affect, although acetylcholine, at relatively high concentrations (≥ 10−4 M) slightly reduced the amplitude of field-evoked contractions.

Microfilariae of Dirofliaria immitis were labelled with 203Hg 2+in vitro and injected into irradiated mice and Beagle dogs. With irradiated mice it was possible to demonstrate microfilariae present in the blood and to detect 203Hg by external counting as long as 28 days after dosing. The 203Hg 2+ label had a half-time of 4–5 days; the amount of stable mercury in the labelling medium strongly influenced the survival of microfilariae in vivo. In dogs, external counting showed the lungs to be a major location of the microfilariae soon after reinjection into the host. Evidence was obtained that labelled microfilariae can circulate; however, the detection of dispersed microfilariae is difficult because of the relative insensitivity of the detecting system. For radiomercury the accumulation of the inorganic form in the liver and kidneys limits the long-term usefulness of 203Hg 2+ as a label if the organism being studied also accumulates in these organs.