1. Dirofilaria aethiops Webber, 1955 has been discovered in African monkeys (Cercopithecus aethiops). Adult worms were found in the interfascicular connective tissue, especially in the thighs; microfilariae were found in the blood.

2. The adult worms are morphologically similar to other members of the genus, from which they differ principally in the structure of the spicules of the male worms. The thickening of the left spicule is complex at the twist; the latter is nearer to the proximal than to the distal end. The right spicule is robust and ends in a cap-like structure.

3. The microfilariae are indistinguishable from those of other members of the genus.

4. In Dirofilaria schoutedeni Vuylsteke & Rodhain, 1938 the left spicule is simpler in structure than the left spicule of D. aethiops, and the twist is nearer to the distal end than to the proximal end. The distal part of the right spicule of D. schoutedeni has longitudinal markings but no cap.

5. D. aethiops has been recorded from Tanganyika, Uganda and Gambia, in Cercopithecus and Colobus monkeys.

6. The anatomy of the female D. aethiops, as it is shown in serial sections, is briefly described.

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.

1. An account is given of the stages of the life history of Dirofilaria aethiops which take place in the monkey and of the transmission of the infection in the laboratory.

2. The microfilariae exhibit nocturnal periodicity in the blood; the number of microfilariae at midday was usually less than 1% of the number at midnight.

3. Aëdes aegypti mosquitoes were fed on monkeys during the evening when there were many microfilariae in the blood. Larvae developed in these mosquitoes and they were ultimately transferred to fresh monkeys by injection of a saline suspension of mosquitoes and infective larvae. In this way six Cercopithecus aethiops and one Macaca mulatto, monkey were successfully infected; seven other Cercopithecus aethiops, one Cebus apella, and one Cercocebus monkey were inoculated, but the worms failed to establish themselves.

4. In the infected monkeys microfilariae appeared in the blood 11 months after the injection of infective larvae. The number of microfilariae then increased for 8–12 months. Subsequently, it decreased to one-tenth of the maximum in 2 years from the first appearance.

5. Post-mortem examination showed that the adult worms live in the fascial tissues on or between the muscle bundles, especially those of the thighs. Tissue reaction to the worms is slight and in these monkeys there was no other pathogenic effect of the infection.

6. Adult worms from three of the monkeys were transplanted to two normal monkeys. Microfilariae were found in the blood of one of these and persisted for over 2 years.

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.

1. A description is given of the morphological development of the larval stages of Dirofilaria aethiops in the mosquito Aëdes aegypti.

2. The first-stage larvae migrate from the stomach to the connective tissue in all parts of the mosquito body, where they pass through the inactive ‘sausage’ stages. At 26° C. and 80% relative humidity the first moult takes place about the twelfth day of development and the second moult about the sixteenth day. The third-stage larvae migrate towards the proboscis where they can be found after 18–20 days.

3. The number of microfilariae ingested by the mosquito is approximately equal to the number which would be expected from the numbers in the blood of the monkey and the volume of the blood meal. The death rate of the larvae in the mosquitoes is very high for the first 2 days, but less severe later. Approximately 1% of the ingested microfilariae survive 20 days; at this time two-thirds of the surviving larvae have reached the third stage.

4. Comparison of D. aethiops with other filariae shows that first-stage larvae of different species can often be distinguished by the structure of the tail, which is the same as that of the microfilaria. Second-stage larvae are similar to each other in morphology but develop in characteristic sites in the host. Third-stage larvae differ from each other in the cephalic and caudal papillae.

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.

1. Filarial worms were found in the peritoneal cavity of a monkey (Macaca speciosa) from Bengal. They were identified as Dipetalonema digitatum (Chandler, 1929).

2. The microfilariae were unsheathed and showed a well-marked nocturnal periodicity in the blood.

3. No development of the microfilariae was detected in Aëdes aegypti, A. albopictus, Anopheles quadrimaculatus or An. stephensi, but only a few mosquitoes were observed.

4. Six female worms and one male were transplanted into the peritoneal cavity of a rhesus monkey (Macaca mulatta). Ten weeks later microfilariae were found in the blood of the monkey and they persisted for at least 16 weeks.

5. Filarial worms (Dipetalonema gracile) were discovered in the peritoneal cavity of a monkey (Cebus apella) from Brazil.

6. The microfilariae were unsheathed and were found in the blood. They showed no periodicity.

7. No development of the microfilariae was detected in Aëdes aegypti, A. albopictus, Anopheles maculipennis atroparvus or An. stephensi.

8. No pathological lesions due to either of these worms were detected in the monkeys.

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.

In 1952 and 1953, 798 specimens of Peromyscus maniculatus, Microtus pennsylvanicus and Clethrionomys gapperi were examined for total louse populations. Two species of sucking lice, Hoplopleura acanthopus and H. hesperomydis, were found on these species. H. acanthopus was found almost exclusively on Microtus pennsylvanicus and Clethrionomys gapperi, and Hoplopleura hesperomydis was found almost exclusively on Peromyscus maniculatus.

Contamination appears to account for the apparently abnormal associations. The rates of infestation varied from host to host and from year to year. In general the higher infestations were found on host populations which were stable or declining, and the lower rates were on hosts which were increasing in density. Microtus pennsylvanicus had the highest infestation rate followed by Peromyscus maniculatus, with Clethrionomys gapperi nearly free of lice.

The age of the host apparently had little to do with rate of infestation or population size.

The louse populations were made up of about equal numbers of adults and nymphs. The adult sex ratio was, in each sample, unbalanced in favour of the females.

The average population size varied between sexes of host and years. The male hosts had a higher average population than the female.

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.

1. NR bodies show special affinity for neutral red. They are rounded or irregular in outline, measuring 0·25–12·5µ in diameter.

2. In fixed preparations NR bodies appear as spherical and vacuolated structures.

3. RNA is present in abundance in mature NR bodies, but while DNA is present in variable amount, the Feulgen technique shows that in their very young stage NR bodies are rich in DNA.

4. Glycogen is absent from the NR bodies, but Hale's technique provides evidence that the hyaluronic acid type of polysaccharide is present in them.

5. By Gomori's modified technique the presence of alkaline phosphatase in the NR body was demonstrated.

6. The mature NR bodies multiply by a process of budding. Small buds or spherules rich in DNA infect fresh spermatogonial cells, the latter being converted into the ‘pathological cells’ of Hertig.

The genus Pneumostrongylus was erected by Münnig (1932) to accommodate the species, P. calcaratus, recovered from the lungs of the common impalla (Aepyceros m. melampus) from the Transvaal. Another species, based on the tail piece of a single male lungworm, was described by Dougherty (1945), from the common white-tailed deer, Odocoileus v. virginianus, from North America. The present species, P. ovis, is based on tail pieces of three male specimens which were recovered from bronchioles of sheep and goats at Murree (7000 ft. above sea-level).

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. Oxynema crassispiculum (Sonsino, 1889) has been redescribed and shown to possess two spicules.

2. The genus Numidica Barreto, 1919 has been shown to be synonymous with the genus Oxynema von Linstow, 1899.

3. The genus Oxynema has been redefined and a synonymic list is given of the species that it now contains.

4. Oxynema typicum Kreis, 1940 is considered to be a species incertae sedis.

5. Baylisnumidica petrodromi (Baylis, 1934) has been redescribed and shown to belong to the genus Parasubulura Berghe & Vuylsteke, 1938.

6. The family Parasubuluridae is reduced to subfamily rank, and placed in the family Subuluridae.

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.

An account is given of the bacterial flora isolated from the blood-sucking Reduviid bugs, Triatoma infestans and T. protracta, and the predatory Reduviid, Sinea diadema. The micro-organisms which have been found in Triatoma spp. differ from that found in Rhodnius prolixus (Actinomyces rhodnii), in both specific identity and in their relation to the cells of the mid-gut. The symbiont occurring most frequently in T. infestans has been identified as a diphtheroid organism resembling Coryne-bacterium hofmannii, and sections show this organism inside vacuoles within some of the endothelial cells of the insect's intestine. The organism occurring in R. prolixus, on the other hand, cannot be found in this situation, but remains in the lumen of the gut. While the occurrence of the bacteria found in T. infestans in so intimate a connexion with the cells of its host seems to suggest a more highly organized state of affairs, T. infestans does not show the fixed association with one species of micro-organism which is shown by R. prolixus. Other bacteria occur commonly in T. infestans, although they do not occur in cell-vacuoles; and the range of bacterial types is so great that it seems unlikely that the species recorded in this paper are the only ones that may occur. The presence of these other bacteria may be due either to the anti-biotic action of the Corynebacterium sp. being weaker than that of A. rhodnii, or to masking of the anti-biotic action by the cell wall that encloses the organisms. The situation in R. prolixus shows clearly that a constant symbiotic association with a micro-organism can be maintained without the presence of specialized organs of the mycetome type.

With regard to the predatory species, no general conclusion can be reached on the evidence so far available. Compared with the blood-sucking Reduviids, insects of this kind usually have powerful proteolytic enzymes secreted in the anterior mid-gut, while the same region of the blood-suckers is a simple storage and concentration sac, digestion taking place lower down the intestine. Thus the region of the gut where bacteria are found in blood-suckers might not be a favourable situation for them in predatory bugs. Hence it is perhaps significant that most of the few successful isolations from a predatory type were from the rectum of the insect. It is the usual opinion that insects with a predatory diet do not need bacterial symbionts, but the aim in examining the predatory Reduviidae has been to find out whether they show a condition which might have evolved into that found in their blood-sucking relatives. The search is still in progress for a rather unspecialized type of predatory Reduviid in which the salivary and anterior mid-gut digestion is less strongly developed than in those species which have been available for study up to the present.

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.

Toxoplasma ‘Nicolle et Manceaux’ has been examined in the electron microscope in in toto preparations from tissue cultures.

The extracellular as well as the intracellular forms of the parasite are too thick for an adequate penetration of the electron beam, and the inner structure of Toxoplasma is not revealed in these preparations.

The whole parasite is covered by a very delicate, transparent mantle which may extend to form large membranes. They show no structure in the electron microscope. No sheath has been observed which protects the shape of the parasite. Most of the free forms have an irregular surface and tend to become flat and large.

Several pictures illustrate the way in which Toxoplasma penetrates the tissue cells. In the beginning of parasitism the limits between cytoplasm and parasite are difficult to recognize. The region of the cytoplasm around the parasite is gradually dissolved and a vacuole is formed.