P. gallinaceum was cultivated in tissue cultures for 1 year. The cultures showed the same high-grade infection as has been observed previously with Toxoplasma and Trypanosoma cruzi, and made possible new observations upon the living parasite.

It has not been possible to obtain in vitro the passage from the exo- into the endoerythrocytic form.

The parasites can survive in tissue cultures, maintained at room temperature, for 23 days.

Observations concerning the periodicity and the phases of the cycle in tissue cultures are being investigated.

Detailed accounts of the morphology of the elephant louse and of its phylogenetic affinities and origin are given. The main points noted are: The peculiarity of the knobs and plate in the head are described. The mouthparts are described, a notable feature being the rotation of the mandible to 180 degrees. Structural peculiarities of the thorax with the muscles are given. The abdomen is found to consist of eight segments. The alimentary canal is described; no crop has been found. The histology of Weber's organ is given, and it is held that this organ is excretory in function. The structure of the spiracle is described, no spiracular gland has been found. The reproductive organs are described. In the female, the follicular epithelium of the ovary is binucleate and a spermatheca is present. In the male, the testis is bi-follicular. The affinities of the elephant louse are discussed and the creation of a new order, the Rhyncophthiraptera, to accommodate Haematomyzus, is suggested.

A wide variety of nematode species have been observed to invade the central nervous system. They may be located in the meningeal spaces or may penetrate into the tissues of the brain and spinal cord.

The pathological changes resulting from invasion of the central nervous system are influenced by the route of entry, the size and the mobility of the parasite. They may be diffuse or focal and may include haemorrhage, degenerative changes, cellular infiltration and glial proliferation. Such changes may or may not be observed in close association with the parasite.

Symptoms indicating involvement of the central nervous system have long been associated with nematode infections outside the central nervous system. The pathogenesis of these symptoms is obscure, but they may possibly be of allergic origin.

The direct pathological effects on the central nervous system are mainly the result of trauma and are directly proportional to the size and activity of the parasite. The possibility that nematodes may transport viruses into the central nervous system is briefly discussed.

1. Experimental infections in mice showed that the larvae of Toxocara canis, T. mystax, Ascaris devosi, A. columnaris and Toxascaris transfuga reached the brain of mice; the larvae of Ascaris lumbricoides, A. suum, Parascaris equorum and Toxascaris leonina were not recovered from the brain. The larvae of T. canis, T. mystax, T. transfuga and A. columnaris remained hi the brain of mice for several months.

2. Larvae reaching the brain produced characteristic haemorrhages on the surface of the cerebral hemispheres in the early stages of infection. It was concluded that the larvae reach the brain via the arterial blood stream, leave the arteries at the point where their diameter approximates that of the larvae, i.e. mostly on the surface of the brain, and penetrate into the brain from the subarachnoid space and chorioidal tissues.

3. The larvae of T. canis were found to occur in the brain of mice in relatively greater numbers than the larvae of other species, but only very rarely caused nervous symptoms. The larvae of T. canis and T. mystax showed no growth in the brain.

4. The larvae of A. columnaris (skunk) frequently caused nervous symptoms in mice, the effect appeared to result from traumatic damage due to the relatively large size attained by these larvae about 3 weeks after infection.

5. The brain of infected mice showed very slight changes consequent upon infection with larvae of T. canis. These larvae moved actively through the tissues; they incited little or no cellular reaction, but left haemorrhagic tracks. The larvae of A. columnaris also moved actively; when in the extended state they were usually found in normal tissue; when coiled, they were often associated with a necrotic focus infiltrated with leucocytes.

6. After experimental infections of dogs with larvae of T. canis, two out of twelve infected animals harboured larvae in the brain. No natural infections with these larvae were found in the brains of dogs and cats. After experimental infection, larvae of T. canis were found in the brain of mice, rats and guinea-pigs, but not of rabbits.

7. Larvae of A. suum were recovered from the cerebrum of one pig suffering from posterior paralysis, but not in an experimentally infected pig.

8. No larvae of P. equorum were found in the brain of foals in natural and experimental infections.

Wild Stomoxys calcitrans flies were dissected in search of developmental larvae of Setaria cervi without success.

S. cervi worms were implanted intraperitoneally into rabbits and live microfilariae were recovered from the blood.

Morphological descriptions are given of the larvae from the blood of rabbits and of the adult worms taken from slaughtered cattle.

The genus Paradilepis Hsü, 1935 syn. Meggittiella Lopez-Neyra, 1942, is defined as follows (Hsü, 1935, p. 536): ‘Dilepididae. Rostellum armed with a double crown of hooks. External segmentation little marked. Genital pores unilateral. Genital ducts pass dorsal to excretory vessels and to nerve. Testes few in number, situated to either side of the female glands. Uterus sacciform, little lobed. Parasites of birds.’

The new species of Trypanosoma described in this paper is parasitic in the blood of Ophicephalus ( = Ophiocephalus) striatus Bl., an air-breathing teleostean ‘Serpentfish’ found extensively in the fresh waters of India. This fish is one of the important food-fishes of India, especially in areas far away from the sea, which are mainly served by inland fisheries. It is equipped with an elaborate accessory air-breathing organ and therefore survives when taken out of water and kept in a moist condition. This hardiness of the fish has made it a popular item of diet since it is available in the hottest months of the summer in a fresh condition or even alive. With the expansion of the inland fisheries of India the importance of fishes of the genus Ophicephalus is also on the increase.

1. Spores of Nosema apis nearly all germinate within 30 min. after entering the ventriculus of the honeybee.

2. The cause of germination in vivo remains unknown, but is probably not a change of osmotic pressure or pH and is probably not due to anaerobic conditions or an enzyme. The agent causing germination is probably unstable and is destroyed when removed from the bee.

3. The anterior end of the ventriculus receives an initial heavy infection and the circumstantial evidence which this provides supports the theory that a free living ‘planont’ stage does not exist but that the parasite is injected directly into the host cell from the spore via the hollow polar filament.

4. The central region of the ventriculus which contains many granules of calcium phosphate receives the lowest initial infection. It is considered possible that the granules inhibit the initial rapid development of the parasite by maintaining an unfavourably high level of pH until they are eventually dissolved by the slowly developing organism.

1. The larva and nymph of Rhipicephalus pulchellus are described for the first time and comments are made on the degree of variation in structure seen amongst adults of a single generation.

2. Information on various aspects of the biology of this tick and on classification is given.

This work started in May 1950 and is part of a wider study of parasite populations on lowland pastures.

An account of observations made on ewes has already been given (Crofton, 1954), and the present paper deals with observations made on lambs from the same flocks. It is realized that a proper approach to parasite problems in sheep entails consideration of the flock as a whole, but for convenience, the observations made on different age groups have been described separately. It is for convenience, also, that pasture contamination is only considered briefly here. Later an attempt will be made to consider parasite populations on a lowland farm as a dynamic system of interacting factors.

Some of the reindeer (Rangifer tarandus) introduced into Scotland from Northern Sweden have become infested with the deer warble fly Hypoderma diana and the deer ked Lipoptena cervi.

Evidence is presented which suggests that the larvae of H. diana proceed to their final site on the back of the host by way of the neural canal, and in this way probably caused the deaths of two reindeer in the winter of 1953–4.

A detailed analysis is presented of the frequency with which various bands of spines occurred on second-stage larvae of H. diana. An analysis of the number of chitinous rings in the two posterior spiracles on second-stage H. diana larvae showed that in any individual larva the two numbers were not independently determined.

On reindeer L. cervi produced puparia in December.

In this paper two new species of Acarina are described, the first a new species of Pterygosoma from a West African agamid lizard and the second a new species of Schöngastiella from two West African rodents. In addition, several new records of Acarina are given, most of these from the Ethiopian region of Africa. The writer wishes to extend his thanks to all those who have contributed material, and in particular Mr W. Crewe and Dr R. Taufflieb.

In January 1954 I received from Dr Harry Hoogstraal of the United States Naval Medical Research Unit no. 3, Cairo, Egypt, a collection of ticks for investigation. In the monograph of Nuttall, Warburton, Cooper & Robinson (1911) these specimens were run down to Ixodes ugandanus Neumann, but in view of the constant differences between them I recognize the present material as a new species. I assign the name hoogstraali to them in consideration of Harry Hoogstraal's kindness and generosity in supplying me with tick material. Unfortunately the entire collection consists of females.

In the course of examining some material from small mammals collected in Denmark, the British Isles and the Channel Islands, it has become evident that comparatively little is known of the species of Ixodes involved. A recent paper by Visotzkaya (1951) on the biology of the mouse tick, I. trianguliceps Birula, 1895, is the only one of its kind. Unfortunately, this paper is written in Russian and is comparatively inaccessible.

Non-splenectomized mice developed acute infections of Eperythrozoon coccoides after inoculation, but were then immune to re-infection. Splenectomy evoked acute infections that were heavier and longer in duration than the primary infection; during this phase, the parasites doubled in number in about 5 hr. The presence of splenic tissue transplanted subcutaneously did not prevent this evocation by splenectomy.

The number of eperythrozoa decreased rapidly after the peak of infection had been reached, but no immune factor was detected in the blood. No immune factor or infection was transmitted from mother to offspring through the milk.

Citrated blood remained infective for 11 days at 3° C., for 17 hr. at 16–17·7°C. and for 3 hr. at 37° C. It was not infective after 24 hr. at either 24° C. or 16–17·7°C., or after 5 hr. at 37° C. Parasitized blood was not infective after drying.

Citrated blood was infective to mice when given by mouth, but was not infective when applied externally. Urine and faeces were non-infective.

Eperythrozoa remained infective when infected blood was diluted with twice its volume of water and left for 24 hr. at 3° C. Phenol, 0·5%, rendered citrated blood non-infective in 1 hr. Neoarsphenamine, 0·1%, reduced the infectivity of citrated blood in 16 hr., and rendered it non-infective in 26 hr.

Cortisone did not affect the course of infection of E. coccoides in mice when given subcutaneously, 1·0 mg. per 20 g. mouse, once daily for 6–9 days.

Concurrent infection with Plasmodium berghei evoked relapses of E. coccoides during the terminal stages of the P. berghei infection.

1. Eleven strains of Entamoeba histolytica were isolated from contact carriers and all proved non-invasive to rats.

2. Three strains from cases showing symptoms proved invasive to rats.

3. The treatment of murine infection with non-invasive strains with emetine hydrochloride shows that most of them were successfully cured with six daily oral doses of 2 mg./kg., though one was not susceptible to this dose. Another proved refractory to 4 mg./kg.

4. The results of previous work with kittens are discussed in the light of the present observations.

Although many interesting observations have been made upon gametogenesis in Haemosporidiidea many fundamental problems await solution. Our knowledge of the nuclear changes occurring during the development of the gametes and the fertilization of the female gamete is still incomplete. Little is known of the factors which control gametocyte production, though there is evidence that in some species, i.e. Leucocytozoon simondi and Haemoproteus columbae in the duck, it is influenced by the physiological stage of the host. The type of host and the method of transmission have also been shown to affect the numbers of gametocytes formed in some species. No correlation has been found in Plasmodium, the genus in which this subject has been studied extensively, between acquired immunity and gametocyte formation. Although a broad relationship has been demonstrated in Plasmodium between the density of gametocytes in the blood and the oocyst rate and density assessed in susceptible mosquitoes, hosts heavily infected with apparently ripe gametocytes may prove non-infective to susceptible mosquitoes. In birds heavily infected with P. gallinaceum, serum taken at the peak of parasitaemia has been shown to affect adversely the infectivity of gametocytes to mosquitoes. Pamaquin and primaquine, in small doses, inhibit the development of gametocytes completely, whereas proguanil may not prevent the formation of oocysts though it inhibits their subsequent development. High densities of gametocytes have been observed in patients treated with proguanil or sulphamethazine. An actual in crease in the number of gametocytes produced, as compared with the untreated control strain, was observed in strains of P. gallinaceum in process of developing resistance to sulphadiazine, proguanil or 2:4-diamino-6:7-diisopropylpteridine as a result of treatment with those drugs.

During the course of preliminary studies on the helminth fauna of local freshwater fishes two species of Crepidostomum, obtained from the intestine of brown trout, were identified as C. farionis (Müller) and C. metoecus Braun. Although C.farionis is a common parasite of the fresh-water salmonoid fishes of the Northern Hemisphere, in Ireland it has been recorded only from trout (Salmo trutta). The first Irish specimens were recorded by Southern (1912) as Stephanophiala laureata (Zeder), and came from fish from a stream in Clare Island and from the Owenwee River, Westport. Later, Vickers (1951) found that trout from the River Moyola, Co. Londonderry, and River Ravarnett, Co. Down, were infected with this species. Prior to the present study, C. farionis was the only representative of the genus to have been recorded from the British Isles. C. metoecus is therefore a new record, not only from Ireland, but from the British Isles as well. Elsewhere it is known to occur in Sweden [ = C. suecicum Nybelin, 1933], Austria, and possibly also in Thuringia, where cercariae were found which Nöller (1928) assigned to C. metoecus.

1. Adult S. mansoni worms were extracted in Coca's solution at various temperatures by different methods. The most potent antigen was obtained by extracting a worm suspension, diluted 1:500, at 37° C. for 1 hr., with vigorous shaking at 10 min. intervals, followed by 23 hr. at 28° C. Second extraction of worm samples gave highly active material and third extractions also contained antigen.

2. Complement-fixation tests, performed with the sera of twenty-five patients with chronic bilharziasis and twenty-five healthy subjects showed that the most specific results were obtained with either the first two extracts of worms, suspended in 100 parts of Coca's solution, and extracted for 1 hr. at 37° C. and 23 hr. at 28° C., or with the first extract of worms, suspended in 500 parts and extracted in the same manner.

3. Samples of an extract in Coca's solution were preserved for 170 days by different methods, and their activity was tested at approximately monthly intervals. The antigen, with or without the addition of 0·1% cysteine, retained its titre for 1 month, when kept in the refrigerator. Freezing, or lyophilization of the extract caused a rapid drop in titre.

4. Titration of extracts of lyophilized worms, from freshly opened ampoules, showed that a constant titre was retained for 3½ months followed by a slight drop after 5–6 months. The worm powder retained its antigenic potency when kept, thoroughly desiccated, in the refrigerator for 4 months, but lost it in 40 days when partial rehydration occurred.

The genus Eucampsipoda was created by Kolenati in 1857 for Eucampsipoda hyrtlii, the common parasite of Rousettus aegyptiacus, and Nycteribia fitzingeri Kol., 1856, which he later considered as synonym with N. aegyptia Macquart, 1851. In his paper of 1863 Kolenati gives illustrations of E. hyrtlii, but not of E. aegyptia as he had in the meantime lost his specimens. Macquart's description does not permit the recognition of the species, and it is even doubtful whether he was dealing with an Eucampsipoda at all. Speiser (1901) adds only a few details to Kolenati's description of E. hyrtlii, but introduces an unfortunate complication by incorrectly identifying specimens from Burma and Sumatra as E. hyrtlii. Later (1908) Speiser identified specimens from the Comoro Islands as E. hyrtlii, but this record has also become doubtful, as will be shown later. Scott (1914) accepts Speiser's identification of the Indonesian material as E. hyrtlii, and describes and figures a female specimen from Ceylon as E. hyrtlii, which is in fact E. latisternum Schuurm. Stekh. Scott (1925) identified specimens from South Africa as E. hyrtlii which on re-exaniination proved to belong to a new species. He also mentions Madagascar as a locality for E. hyrtlii without giving details. The distribution of E. hyrtlii was thus apparently extremely wide, throughout Africa, from the Cape Province to Egypt and beyond into Palestine, Comoro Islands, Madagascar, Ceylon, Burma and Sumatra.