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A ocorrência de hemagregarinas no sangue dos sapos que examinamos (Bufo crucifer, B. marinus e Melanophryniscus moreirae) revelou-se extremamente rara; apenas um exemplar de B. crucifer procedente de Manguinhos (Rio de Janeiro, Guanabara) apresentou-se parasitado. As formas sanguíneas encontradas eram intra-eritrocitárias, medindo em média 10,8/ 3,6µ; não as identificamos como trofozoítos ou gametócitos e discutimos este fato. As hemácias parasitadas tinham dimensões normais, porém podiam ter o núcleo deslocado. Supomos ser esta a primeira referência a hemogregarinas neste hospedeiro. Não encontramos identidade entre as formas que descrevemos e aquelas referidas em outras espécies de sapos; fornecemos uma lista das hemogregarinas achadas nestes hospedeiros. Denominamos provisoriamente os parasitos que encontramos Haemogregarina "sensu lato", até que novos dados sobre seu ciclo evolutivo sejam conhecidos. The occurrence of hemogregarines in the blood of Brazilian toads that we have examined (Bufo crucifer, B. Marinus and Melanophryniscus moreirae) has displayed very scarce; only one specimen of B. crucifer from Manguinhos (Rio de Janeiro, Guanabara) was infected. The blood forms that we found were intraerythrocytic, averaging 10,8 by 3,6µ; we did not differenciate them as thophozoites or as gametocytes and we discuss this fact. The infected erythrocytes were not hypertrophied and their nucleus was normal and sometimes displaced. We think that it is the first reference to hemogregarines in this host. We did not evidence identity among the forms that we described and those reported in other species of toads; we give a list of hemogregarines found in those hosts. We provisorily named the parasites that we found Haemogregarina "sensu lato", until new data about their life cycle become known.

Significant structural differences are observed between the chloroquine-resistant Vietnam (Smith) strain and the chloroquine-sensitive Malaya (Camp-Sadun) strain of Plasmodium falciparum. The Vietnam strain shows subpellicular microtubules in the gametocyte, granular aggregates of the nucleus and enlargement of food vacuoles in the gametocyte and asexual form, while the Malaya (Camp-Sadun) strain lacks such findings. These differences are attributable to genetic variation rather than to drug resistance.

SYNOPSIS. The blood of each of 95 turtles (8 species) collected from southeastern Louisiana was infected with some or all of the merogonic stages and gametocyte stage of Haemogregarina pseudemydis n. sp. Five species of turtles harbored Pirhemocyton chelonarum n. sp. Turtle Haemogregarina and Pirhemocyton are locality records for Louisiana. Pirhemocyton is reported for the first time in turtles and in the continental U.S.A.

The antimalarial activity of the dihydrofolate reductase inhibitors, chlorguanide and pyrimethamine, against gametocytes and sporogony of the simian parasite, Plasmodium cynomolgi was tested. Plasmodium cynomolgi infected rhesus monkeys (Macaca mulatta) were treated orally with multiple doses of chlorguanide (5.6 or 11.3 mg base/kg/Day X5) or a single dose of pyrimethamine (3 mg base/kg). Batches of mosquitoes (Anopheles maculatus) were allowed to feed immediately prior to and at appropriate intervals after drug administration. The effects of the drugs on the developmental stages of the parasite were assessed within the mosquito host. The results indicated that sporogony was interrupted in mosquitoes fed 1 hr after initial dosing with chlorguanide. With pyrimethamine, a clear-cut sporontocidal action was shown as early as 15 min after the drug was given. Both compounds inhibited further development of young oocysts and successive batches of mosquitoes fed 1 hr or more after medication ware consistently negative for sporozoites. Administration of either compound in the indicated doses did not prevent exflagellation, zygote or ookinete formation. However, the behavior of the latter forms was apparently altered by the action of the drug. There was a marked retarding effect in the formation of ookinetes in mosquitoes fed 24 hr after initial medication and thereafter. The schizontocidal and gametocytocidal action of chlorguanide was more evident than it was in pyrimethamine.

Five controlled experiments were performed to test the validity of the theory of nocturnal infectivity of gametocytes of Plasmodium. Two gave equivocal results probably because synchronicity of parasitaemia was low; the remaining three, in which a langur strain of P. cynomolgi was used, largely confirmed Hawking's work and in particular demonstrated the much greater production of oocysts after midnight as compared with midday feedings.

The antimalarial activity of RC-12 (1,2 dimethoxy-4-(bis-diethyl-aminoethyl)-amino-5-bromobenzene) and WR 14,997 (1-aminocyclopentane-carboxylic acid) against gametocytes and sporogony of Plasmodium cynomolgi was studied using Macaca mulatta monkeys and Anopheles maculatus mosquitoes. The effect of the drugs on the mosquito stages of the parasite was assessed both after treatment by gavage of infected monkeys and direct administration in sugar solutions to plasmodial-infected mosquitoes. Single- or multiple-dose treatments of RC-12 (25 mg/kg a day) were equally effective against gametocytes and sporogony of the parasite. Mosquito infection was interrupted within 8 to 24 hours following initial treatment. Feeding of RC-12 directly to infected mosquitoes resulted in no discernible effects on oocyst development and/or sporozoite formation in the mosquito. The salivary glands of drug-treated mosquitoes displayed marked morpho-pathological alterations as a result of drug ingestion. Repeated daily doses of WR 14,997 (60 mg/kg or 100 mg/kg) had no significant gametocytocidal, sporontocidal, or causal prophylactic activity against P. cynomolgi infections after being administered to the monkey host. In contrast, WR 14,997 exhibited a marked sporontocidal action against the parasite when the drug was administered with the mosquito diet. These results failed to support the assumption that there is a correlation in drug response between the sporogonic cycle of the malaria parasite in the invertebrate host and the tissue stages of the same parasite in the vertebrate host, when the drug was fed directly to the mosquito. However, there appears to be a direct relationship between the effect of the drug on the gametocytes and tissue stages when the drug is administered to the vertebrate host prior to mosquito feeding.

Glycogen proved to be absent in the malaria parasites (Plasmodium and Hepatocystis) by applying cytochemical methods; while in the piroplasms (Theileria and Babesia), and in Hepatozoon glycogen could be demonstrated by using the same methods. A strong positive reaction for polysaccharides was obtained in the residual masses of Hepatozoon sciuri, and H. balfouri; while a negative reaction was obtained in the residual mass of Plasmodium. A positive reaction for polysaccharides was obtained in the following structures: the wall of the oocysts of Plasmodium, the gametocyte capsules of Hepatozoon sciuri and Hepatozoon sp., the sporoblast capsule of H. sciuri, and the polar areas of the gametocyte of H. balfouri.

1. 1. An account is given of a series of therapeutic trials with paludrine carried out at Horton Hospital, Epsom, against infections with a strain of P. falciparum obtained from an African child resident. in Lagos, Nigeria, West Africa. 2. 2. Paludrine effectually controlled the clinical attack produced by infections with this strain of parasite, but its action in this respect and in clearance of asexual parasites from the peripheral blood was somewhat less rapid than that achieved with mepacrine or quinine. 3. 3. Paludrine without reinforcement failed to effect radical cure of infections with this strain, nine out of ten cases so treated relapsing within 3 weeks after completion of the course. This finding was in marked contrast with the results reported by FAIRLEY and his colleagues in their researches on infections with New Guinea strains of P. falciparum . 4. 4. Radical cure of infections with the Lagos strain of P. falciparum was effected in a limited series of cases treated with paludrine reinforced with mepacrine or with quinine on the first day of treatment, and with quinine alone. 5. 5. Following a course of paludrine mg. 300 twice daily for 10 days, gametocytes were found to be non-infectioe to mosquitoes for as long as they continued to be present in the peripheral blood in sufficient numbers for infection to occur. 6. 6. Reinforcement of a 10 days' course of paludrine with mepacrine given on the first day of treatment shortened the average duration of pyrexia and clinical symptoms by approximately 24 hours. Similar reinforcement with quinine did not have this effect. 7. 7. It is considered that a course of paludrine mg. 300 twice daily for 10 days, reinforced with mepacrine mg. 900 given in three doses on the first day of treatment and followed by a maintenance dose of paludrine mg. 100 daily for the ensuing 6 weeks would fulfil the main objectives in the treatment of falciparum malaria, namely, rapid termination of the clinical attack, a high radical cure rate, sterilization of gametocytes and minimum risk of injurious side effects.

Summary and Conclusions The study here reported had for its object the investigation of the effects of quinine and plasmochin on infections with Plasmodium circumflexum, and comparison of the results with those already obtained by similar treatment of infections with the other four species of avian malaria (Plasmodium capistrani excepted). A total of fifty-five female canaries were used in the treated series. The results may be summarized as follows: 1. Basing the list which is given below partly on the data reported in the present paper and partly on data previously reported, the susceptibility of the five species of avian plasmodia here considered to treatment with quinine and plasmochin appears to be as follows, the most susceptible being given first: Quinine Plasmochin 1. Plasmodium rouxi 1. Plasmodium elongatum 2. Plasmodium praecox Plasmodium rouxi 3. Plasmodium cathemerium 2. Plasmodium praecox 4. Plasmodium circumfiexum 3. Plasmodium circumfiexum 5. Plasmodium elongatum 4. Plasmodium cathemerium It should be noted that in the first list (quinine) the differences between Praecox, cathemerium and circumflexum are very small, and that this is also true of praecox and circumflexum in the second list. Elongatum and rouxi are placed at the top of the second list, and rouxi heads the first list, chiefly because infections with this species could be readily sterilized with the drug in question. Cathemerium and circumflexum occupy the positions they do (even though plasmochin is effective in removing parasites from the peripheral blood in a relatively short time) largely for the contrary reason; in other cases the percentage of parasite-free days was the chief factor governing the place of the species in the scale. 2. As with the other species, Plasmodium circumflexum is more amenable to plasmochin than to quinine. When sterilization is not brought about relapse within a month generally occurs, but does so less frequently than in praecox infections, and may be deferred for two months or even longer. This is correlated with the fact that the parasite-level in chronic infections of circumflexum is generally established at a much lower level than in the case of praecox, and is to be compared in this respect only to cathemerium. 3. Plasmochin in combination with quinine is apparently no better than when used separately, and may even be less satisfactory—due possibly to quinine intoxication. 4. As with the other species, treatment during the incubation period is much more effective than when postponed until parasites appear. A considerable proportion of cases may be completely aborted in the former case, as demonstrated by continued freedom from relapse and by subinoculation, with subsequent reinfection, but so far no case in which parasites had already appeared has been sterilized. 5. There is little evidence that gametocytes are either more or less susceptible to plasmochin and quinine than the asexual stages. 6. Study of the rates of reproduction of the different species, and other peculiarities of the life-cycle, suggests that the degree of susceptibility to drug therapy may depend in large part on these factors—particularly in the case of plasmochin.

The survival of Plasmodium lophurae in vitro, at temperatures of 39.5–42°C., is favored by a balanced salt solution having a high potassium content, by aeration but not by a very high oxygen tension, by an optimal density of parasites per cubic millimeter, by frequent renewal of the suspending medium, by concentrated red cell extract, by optimal concentrations of plasma or serum, of chick embryo extract, of glucose or glycogen, and of glutathione, and probably by yeast extract and a very low concentration of liver extract. In the best preparations, as judged by infectivity, more than 40 per cent of the parasites were alive on the 3rd day, more than 20 per cent on the 4th day, perhaps 1 per cent on the 5th day, and about 0.05 per cent on the 6th day. Evidence was obtained that the parasites had multiplied during the 1st day of incubation.

Blood containing gametocytes of Plasmodium berghei (N.K. 65 strains) taken up by Anopheles stephensi during the infective blood meal and rapidly ejected during the act of engorgement induced formation of large numbers of ookinetes in vitro when the blood was subsequently kept in heparinized capillary tubes for 22–24 hours at 21 °C. A parallelism between ookinete formation in vitro and oocyst development in vivo has been observed in these studies. Aqueous extracts of A. stephensi midguts added to blood containing gametocytes of P. berghei induced fertilization and ookinete formation of P. berghei under similar experimental conditions. Extracts from blood obtained from engorged A. stephensi failed to induce any marked ookinete formation in vitro . Clumping and close adherence of ookinetes has been observed in vitro . Tightly clustered groups of macrogametocytes and macrogametes were noted both in the in vitro blood stained smears and also in some midgut preparations from infected A. stephensi , 22–24 hours after the infective blood meal. It is assumed that ookinete agglutination originates in earlier adherence and clumping of the fertilized gametes.

IN controlled experiments with Culex bit” niorhynchus carried out during the past seventeen months, we have observed what we are unable to distinguish from the complete cycle of development of the parasites of benign and sub-tertian (malignant) malaria in laboratory-bred females fed on gametocytes of Plasmodium falciparum and P. vivax respectively. Presumptive sporozoites accompanied by a stomach cyst were also observed in an insect which was fed on gametocytes of P. malari” , the parasites of quartan fever, those of sub-tertian being also present in much smaller numbers. Ross's black spores were found associated with sporozoites and cysts in several sub-tertian infected, and in one benign tertian infected, insect. These appearances were absent in laboratory-bred controls which had had no blood meals.

A second species of monkey Plasmodium of the New World is described from the howler monkey Alouatta`fusca GEOFFROY, 1812, captured in Itapecirica, São Paulo, Brazil. The new species differs from Plasmodium brasilianum GONDER et VON BERENBERG-GOSSLER, 1909 by following characters: 1st. Almost constant presence in the blood cells of granulations of the same type as SCHÜFFNER dots. 2nd. Considerable hypertrophy of the parasitised cells. 3rd. Greater number of merozoites after schizogony with an habitual minimum of 16 elements in contrast with the maximum of 16 in Plasmodium brasilianum. 4th. Extreme rarity of band forms. This morphology strongly suggests an infection of the benignan tertian type. To this new species the name of Plasmodium simium, sp.n. is proposed.

SYNOPSIS. The teiid lizard Ameiva ameiva praesignis in Panama is parasitized by 2 species of Plasmodium: P. cnemidophori Carini and P. diminutivum sp. n. The Panamanian strain of P. cnemidophori has thick macrogametocytes which are larger than the oval microgametocytes, and schizonts which contain 42–119 nuclei. P. diminutivum is characterized by round to oval gametocytes which are usually smaller than the host cell nucleus; fan-shaped schizonts with 4–6 nuclei; and prominently vacuolated young stages, with a thick band of chromatin along the periphery of the vacuole.

SYNOPSIS Plasmodium gonatodi sp. nov. is described from Gonatodes albogularis fuscus of eastern Panama. It is characterized by elongate gametocytes and polymorphic schizonts containing 12-46 nuclei when apparently mature. Both proerythrocytes and erythrocytes are commonly parasitized, host cells are hypertrophied and distorted, and their nuclei are displaced. Prematuration sexual stages may be irregularly shaped and larger than mature gametocytes. Plasmodium diploglossi Aragao and Neiva, 1909 is reported from Mabuya mabouya in eastern Panama, and Plasmodium morulum sp. nov. is described from this host. P. morulum usually parasitizes immature erythrocytes, and is characterized by lenticular or oval to round gametocytes, and schizonts with 14-40 nuclei usually arranged in a globular mass. Host cells are slightly hypertrophied and distorted, and their nuclei are usually displaced. Inoculation of infected blood into clean hosts produces numerous schizonts in white cells as well as in the erythrocyte series. Pigment in both P. gonatodi and P. morulum, if present, consists of a few minute dark dots which do not meet the polarized light test for hemozoin.

SYNOPSIS. Leucocytozoon neavei and Leucocytozoon caulleryi were found in guinea fowl in Tanzania and Leucocytozoon schoutedeni in chickens. The minimum time required for sporogony of L. neavei at approximately 20 C was ∼7 days in Simulium adersi and Simulium nyasalandicum. Gametocytes of L. neavei, which appeared mature, were seen in the peripheral blood of guinea fowl chicks 14 days after experimenal inoculation with sporozoites from S. adersi or S. nyasalandicum. Sporogony of L. schoutedeni was followed in “Simulium impukane,” S. adersi, Simulium vorax and S. nyasalandicum. Oocysts were ∼12 μm in diameter. Sporogony of some individuals was completed in 6–7 days at 20 C. Each oocyst produced ∼50–60 sporozoites. Gametocytes were detected in the peripheral blood of a chicken 10–14 days after experimental inoculation with sporozoites of L. schoutedeni from S. adersi and “S. impukane.”

Summary and Conclusions In a field study in South Carolina, Anopheles quadrimaculatus mosquitoes were applied to native cases of malaria in Negroes to determine the infectivity of such malaria cases. Of 142 feedings upon Plasmodium falciparum patients, 21 showed infections. Of 12,606 mosquitoes dissected, 2.5 per cent were infected. These infections developed normally in the mosquito and in one out of two trials transmission was successful. The majority of the mosquito infections occurred during the months of October through January. Mosquitoes kept at outside temperatures during October and November became infected. One patient remained infective to mosquitoes over an 8-month period. Of the 25 patients showing gametocytes, 64 per cent infected mosquitoes. The gametocyte densities resulting in infections were relatively low, none being over 90 per cmm. Thirteen of the infections resulted when the gametocytes were fewer than 10 per cmm. Patients with asymptomatic parasitemias infected mosquitoes at about the same rate as did those who were symptomatic. As the asymptomatic group is considerably larger than the other, it is concluded that the former is mainly responsible for the transmission of malaria. There were 14 feedings upon P. malariae. Four cases showed gametocytes of a low density at feeding and three lots of mosquitoes were infected. Of 586 mosquitoes dissected, 1.7 per cent were infected. Of nine feedings upon P. vivax, none became infected nor were gametocytes present. It is concluded that the patient with an asymptomatic parasitemia, usually with a relatively low gametocyte density, is the important factor in the transmission and maintenance of P. falciparum and P. malariae malaria in the area studied.

SYNOPSIS. All of 99 adult English house-sparrows, examined in the St. Albans area of Hertfordshire, England, were found to be infected with the organism previously defined by Garnham (1950) as Atoxoplasma. Young birds were found to become infected while still in the nests and as early as 6 days after hatching; there was no evidence to suggest that the parasite was transmitted through the egg. Within a few weeks of leaving the nests, all of 150 fledgling sparrows examined were heavily infected and several trapped birds died from massive infections. All stages of schizogony were found in the lymphoid-macrophage cells of the spleen, bone marrow and liver of these birds; later, as the schizogonic cycle abated, gametocytes developed in similar cells of the liver, lungs and kidney. These gametocytes are of the Eimeria type: the zygote nucleus divides to produce an asporous and polyzoic oocyst containing a large number of sporozoites, and after the rupture of the oocyst these sporozoites invade the lymphocytes and monocytes of the peripheral blood. Transmission of the parasite in the sparrow is thought to take place after the ingestion of infected mites (Dermanyssus gallinae) by the young birds in the nests: unchanged sporozoites were found in smears of these mites that had been fed on infected sparrows. Transmission experiments were impossible due to the complete lack of clean sparrows. The taxonomic status of Atoxoplasma is discussed. The type of life cycle and the production of asporous, polyzoic oocysts indicate inclusion of this parasite in the Order Coccidiida, Family Eimeriidae, Sub-Family Cryptosporidiinae Hoare, 1933. After comparison of the two genera, the author concludes that Atoxoplasma must be regarded as a synonym for Lankesterella. Some previously described species of Atoxoplasma are, therefore, transferred to the genus Lankesterella. The name Lankesterella garnhami nov. sp., is proposed for the parasite in the English sparrow (Passer domesticus domesticus), and Lankesterella serini nov. sp., for that in the canary (Serinus canarius).

SYNOPSIS. New observations are described which confirm the synonymy of Triboliocystis garnhami Dissanaike with Farinocystis tribolii Weiser. The original descriptions have been amplified and combined, and the parasite is shown to have 2 distinct schizogonic cycles, the 2nd of which gives rise to uninucleate gametocytes. After association, the gametocytes each produce 16 gametes. The number of oocysts rarely reaches the expected 16, being usually 8 or 9. It is concluded that the parasite should retain its generic status and be placed according to Grasse's classification (2) in the family Lipotrophidae.

Two vivax-like parasites, believed to be true P. vivax but in abnormal form, are described. The deviation from normal appearances was probably due, it is suggested, to growth in an abnormal environment.

Ducks exposed outdoors in Algonquin Park during the summer became infected with Leucocytozoon simondi and many of them died from the infection in June and July when black flies were abundant. The minimum prepatent period was five and a half days. Young parasites were observed in erythrocytes and lymphocytes; mature gametocytes, as shown by exflagellation of microgametocytes, occurred in round and elongated host cells. Asexual development was observed in the spleen, liver, heart, brain, lung, lymphoid tissue, and pancreas. The schizonts were large and contained, at maturity, more than a million merozoites about 1 μ in diameter. Sexual development of the parasites within two species of black flies was completed in three days at summer temperature. Ookinetes were present in the stomach of black flies about four to six hours after the flies had ingested blood containing gametocytes. Developing oocysts were found free among the stomach contents of flies 40–48 hr. after the blood meal. Sporozoites were observed between 60–70 hr. after the flies had ingested gametocytes. Artificial infections were produced in ducks following the injection of macerated black flies that had fed two and one-half to seven days previously on infected ducks. The resulting infections were less severe than those that resulted from natural infections, although the pattern was similar and a minimum prepatent period of eight days was observed. The asexual cycle was completed in fewer than six days although some asynchronicity was apparent. Artificial infections were produced following the injections of blood, spleen, liver, lung, and bone marrow that were taken from ducks at various intervals following their exposure to natural infection. The minimum prepatent period in these infections was eight days and low parasitemias were produced. Gametocytes survived for at least one week in peripheral blood. Ducks developed some resistance following repeated infections but single infections did not protect ducks that were exposed to infection six weeks later. Heavy infections developed in ducks that were splenectomized. The leucocytosis and anemia associated with infections were measured and recorded.

SYNOPSIS Plasmodium chiricahuae sp. nov. from the Arizona lizards Sceloporus jarrovi and S. clarki is similar to P. mexicanum Thompson and Huff, but differs by having larger gametocytes and smaller erythrocytic schizonts (4-8 merozoites). It produces low-level parasitemia with early appearance of gametocytes. Gametocytes may persist over one year following cessation of erythrocytic schizogonic activity. P. chiricahuae varies in prevalence at different altitudes, being most common between 6000 and 8000 feet. Infected hosts were collected at a maximum of 9200 feet.

1. 1) From extensive clinical and entomological studies carried out for a period of 13 months in the Maprik area of the Sepik District it has been established that a situation of true holoendemicity exists in this area. This view is supported by the following data: Infant Parasite Rate gives a value of 0.015 for the inoculation rate. Adult spleen rate (in males) about 26 per cent., infants and children up to 100 per cent. Parasite rates up to 100 per cent. in infants and toddlers, 33.9 per cent. in adults. 44.6 per cent. of all infections are with P. vivax possibly owing to the absence of the sickle-cell gene from these communities. The dominant vector species is A. punctulatus Donitz with a natural daily survival rate of 87 per cent. It is highly endophilic and endophagous with an average sporozoite rate of 3.3 per cent. The Index of Stability is 2.9, the Basic Reproduction Rate, 1,750. The ruling reproduction rate is 1.15. The critical density of anophelines is 0.0175. 2. 2) An increase in the daily mortality of anophelines in the region of 40 per cent. is required to secure control of malaria. This can only be achieved if the residual insecticide used produces a daily mortality of at least 80 per cent. 3. 3) Under the exceptional conditions prevailing at Maprik it is unlikely that DDT or Dieldrin alone sprayed at 6-monthly intervals will succeed in stopping transmission entirely, but an increase in the frequency of spraying to, say, once every 4 months would succeed. Where transmission is less intense residual spraying by normal methods is more likely to succeed. Dieldrin has a shorter residual action on walls made of plant surfaces than on mud. It is uncertain whether DDT or Dieldrin will be the better insecticide for general use in a large scale control programme in this Territory.

SYNOPSIS. Sexual stages of a reptilian hemogregarine Hepatozoon rarefaciens are described from the hemocoele of a mosquito vector Culex tarsalis. The gametocytes associate within 0.5 hr after biting. Most of the gametocytes then pair off and begin to differentiate. After about 26 hr at 22–23 C, the macrogametocyte usually becomes crescent-shaped with the microgametocyte lying in the concavity. The nucleus of the macrogametocyte enlarges considerably, while the microgametocyte divides into 2 and eventually into 4 spindle-shaped microgametes which are biflagellated. The macrogametocyte increases in size and rounds up to form a macrogamete. Gamete formation is usually completed by 60 hr and fertilization begins soon thereafter. The zygotes develop into the uninucleate oocysts described previously. In some other species of Hepatozoon, gametogenesis has been described as taking place in the stomach of the arthropod vector, with the microgametocytes transforming without cytoplasmic division into non-flagellated microgametes. The occurrence of 2 distinct types of gametogenesis may possibly be a basis for separating Hepatozoon into 2 genera.

The study of the ultrastructure of the blood stages of P.tropiduri Aragao & Neiva, 1909 shows close similarities between this species and P.floridense, another lizard malaria parasite. The absence of a rounded structure in the merozoites of P.tropiduri, and their tendency not to project beyond the original area occupied by the schizont are the ultrastructural characteristics that differentiate the two species.The close relationships of homology between P.tropiduri and the Plasmodium of birds are emphasized, and new evidence on their phylogenetic relationships is offered.P.tropiduri has a mode of ingestion and digestion similar to that of P. elongatum. When the size of the cytostome, the size of the boluses produced by the phagotrophy, and the size of the digestive vacuoles are compared, they are seen to be nearly identical in the two species.The comparative study of the structure of the cytostomes of the merozoites and the trophozoites, and of their relationships with the membranes that limit the parasites, gives new evidence that the external membrane of the trophozoites schizonts, and gametocytes is derived from the host cell.An exflagellatory apparatus is described from the microgametocytes of P.tropiduri, and its relationships with similar structures described from the gametocytes of avian Plasmodium and from Coccidia are discussed.

The relative susceptibility of Aedes aegypti and Anopheles quadrimaculatus to Plasmodium gallinaceum infection was determined in experiments in which paired groups of the two species were fed on chicks with different levels of infection. Mosquito infections were described by the geometric mean of oocyst numbers in infected individuals and the percentage infection in a sample. These parameters were positively related in both species. When the geometric mean of oocyst numbers exceeded 40, A. aegypti manifested total susceptibility; infection incidence in A. quadrimaculatus was always lower than in a comparable group of A. aegypti and a portion of the anopheline population appeared refractory to infection. The changes in incidence, intensity and range of infection in mosquito samples fed at intervals during the course of patent chick infection are described. A. aegypti always had the higher incidence of infection and, in samples fed when gametocyte numbers were low, the infected culicines also had the greater range and intensity of infection. In samples fed at, or near, the peak of gametocytaemia, however, the range and mean of oocyst numbers in infected A. quadrimaculatus equaled or exceeded those in A. aegypti . Gametocyte infectivity declined for both species as gametocyte numbers increased in a developing chick infection and, for A. aegypti only, increased as gametocyte numbers declined in infections progressing to recovery. Transfer of a volume of heavily infected blood, by intravenous injection, to an uninfected chick immediately restored gametocyte infectivity for both species of mosquito. Increase and decrease in infectivity were both more markedly evidenced by changes in the level of A. aegypti infection.

1. 1. There is a real need for a detailed study of hyper-endemic malaria in African villages, in order to provide the necessary background to more summary observations in other parts. 2. 2. A survey of previous work shows that, while a few careful studies of this nature have been made in other parts of the world, Africa is not so fortunate. The previous observations recorded show that the findings in different countries cannot be fitted into a coherent whole. 3. 3. A description is given of the people studied, their diet, and their conditions of life, with some indication of the diseases to which they are subject and of the birth and death rates. 4. 4. There is a high prevalence of A. gambiae in. houses, and a mean sporozoite infectivity of 12-2 per cent. The infectivity has a seasonal rise to 24 per cent., at a time when there is an average of nearly 15 female anopheles to a house. 5. 5. In a detailed clinical description of the course of malarial infection in this untreated population, it is shown that all babies are infected within 5 months of birth, and that all have severe infections. 6. 6. This stage of acute infestation has passed its zenith after 18 months, and is succeeded by a period of malarial instability, during which the parasite count rises and falls irregularly. But symptoms are absent. 7. 7. After puberty symptoms are completely absent, and the general parasite level is a fiftieth or less of that which is present during infancy. 8. 8. The spleen rate is high, being 85 per cent., but it decreases with the parasite rate, as immunity is acquired. The largest spleens are found in babies soon after their first infection. 9. 9. There is a seasonal rise in the parasite infestation of man, which is chiefly confined to the non-immune and partially immune children. 10. 10. Gametocytes are found predominantly in children, at the time when immunity is just beginning to be established. Even if they are present in adults, they occur in very small numbers only. There is a great seasonal rise in the frequency and number of gametocytes in children under 5 years of age. 11. 11. P. falciparum is the dominant infection at all ages, but the other species (including P. ovale) are also present during the first few years of life, and more rarely later. The immunity acquired to P. falciparum is less complete than that acquired to the other species. 12. 12. While children suffer from malaria during the first 2 years of life, and a few die during the first few months, older children cannot be said so to suffer, and no evidence was obtained of any harmful effects from malaria during adult life.

SYNOPSIS. H. canis (James) is reported from three of 36 stray dogs at Singapore and one of 34 palm civets (Paradoxurus hermaphroditus Pallas) from Jeram, Selangor. H. muris (Balfour) was found at Singapore in 10 of 61 examples of Rattus norvegicus (Erxleben) and five of 23 of R. rattus diardi (Jentinck), and is also recorded from six of 139 examples of R. r. jarak (Bonhote) from Pulau Jarak, Straits of Malacca. Neutrophils of P. hermaphroditus containing gametocytes of H. canis exhibit pronounced karyorrhexis, while most of the parasites themselves show signs of pyknosis.