A leptomonad parasite was found in the sap of the tomato and in one unidentified plant, but it has not yet been seen in several others on which the insect feeds.

Interesting characteristics of this Leptomonas are (a) its extreme polymorphism, (b) the development of metacyclic forms in the salivary glands of its insect host, and (c) its alternation between insect and plant host.

Various authors have recorded the seasonal occurrence of different species of nematode parasites in sheep. Some of these (Ross & Gordon, 1936; Gordon, 1950; Taylor, 1934) have been mainly interested in the epidemiology of outbreaks of parasitic disease, but others have recorded the incidence of different species in flocks in which no outbreak has occurred (Gordon, 1948, 1950; Morgan & Oldham, 1934; Morgan & Sloan, 1947; Morgan, Parnell & Rayski, 1950; Parnell, 1954; Parnell, Rayski, Dunn & Mackenzie, 1954; Stewart & Douglas, 1938; Tetley, 1935, 1941, 1949; Wilson, Morgan, Parnell & Rayski, 1953).

1. Nine layers have been identified in the cuticle of Ascaris lumbricoides var. suis under the light microscope and their nomenclature is identical with that of van Bömmel.

2. The inner cortical layer consists of a distinct structure which is seen to be markedly different from the homogeneous layer when fresh frozen sections are examined under phase contrast.

3. Examination of the outer surface of the cortical layer under the electron microscope after layer stripping and sectioning has revealed the presence of a ridged osmiophilic layer which is less than a thousand Ångström units thick.

4. Longitudinal osmium-fixed sections, when examined under the electron microscope, have shown that the external cortical layer has radial striations which appear to link up with the striations which radiate from an aster-like process at the top of the structure arising from the ‘fibrillar layer’.

5. The osmium-fixed homogeneous layer, when viewed under the electron microscope, is seen to consist of fine radial striations.

6. The fibre layers do not show any finer structures when they are examined under the electron microscope. In longitudinal section, they are seen to consist of irregularly shaped fibres without an internal fibrillar structure. Layer stripping shows that they lack the type of periodic structure seen in collagen.

7. The basal lamella is similar, in that the electron microscope does not reveal any finer structures.

Three new parasitic mites—a fur mite, a mange mite, and a nasal mite—were recovered recently on dissolving the head of a specimen of Hystrix africaeaustralis Peters, the South African porcupine, in a solution of potassium hydroxide. The fur mite is being studied by Dr R. F. Lawrence of the Natal Museum. The other two species, the mange mite, belonging to the genus Psorergates Tyrrell, and the nasal mite, belonging to the genus Rhinophaga Fain, are described below.

The life cycle of Nosema helminthorum proceeds as follows (see Fig. 39).

Emergence of the sporoplasm. The spores swallowed by the vertebrate host (sheep) reach the small intestine where the tapeworm (Moniezia) is already present. Here are extruded the filaments with the sporoplasms attached to their tips. These sporoplasms come in contact with the cuticle of the tapeworm at various places, round off and work their way through the cuticle into the tissues of the worm.

Schizogony. They next proceed between the subcuticular cells (3) and start multiplying by binary fission or by multiple division (4, 5, 6, 7). Some of the so-called schizonts are spherical with three to four nuclei (6), while others are elongate plasmodia which give rise to chains of daughter-schizonts by division (7). All these schizonts give rise eventually to faintly staining schizonts in which the nuclei appear to be less compact. Some of these now enter the second phase of schizogony in which elongate fusiform or spindle-shaped cells are ultimately produced (10, 14). The nuclei of these elongate cells divide and move to the opposite poles, and the cytoplasm constricts between them. In this way a chain of fusiform schizonts may be formed (11). The final products of these divisions are fusiform or spindle-shaped cells (11, 15) which are really the precursors of sporonts, in which the nuclei are divided but not separated. These nuclei remain closely associated and eventually fuse either before the sporont stage is reached or later.

Sporogony. The sporonts are ovoidal cells which are generally uninucleate after fusion of the double nuclei of the previous stage. The nucleus is at the centre. Soon a vacuole is formed at the posterior pole, and within it there appears a premetachromatic granule (16) which gives rise to the metachromatic body in the mature spore.

Spore formation. A chitinous spore wall is then secreted (17) and the filament is probably formed at this stage in the central axis of the cytoplasm. The rest of the cytoplasm transforms into the sporoplasm, which surrounds the filament like a girdle (18). The spore now becomes mature and is infective to a new host. It is passed out within the gravid segments of the worm and, when it reaches the exterior, is liberated when the segments degenerate. These spores are quite resistant and probably remain dormant during the winter; they are swallowed by Moniezia-infected lambs in spring, when the cycle is resumed.

It is unlikely that the oribatid mite, which is the vector of Moniezia, plays any role in the transmission of Nosema helminthorum. My experimental studies (to be published later) suggest that the only possible part played by the mite is to carry the spores, accidentally swallowed by it, protecting them till they reach the adult worm already present in the intestine of the vertebrate host.

Ixodes thompsoni was established on three females collected from a cat on Lundy Island (Arthur, 1955). Further collections on Lundy from a cat since that date suggest that the species is relatively common on the Island and we now have the following specimens: cat, Lundy Island, 16. iii. 1955 (1955/81), two females; cat, Lundy Island, 20. iv. 1955 (1955/30), two females with two males in copula; cat, Lundy Island, 31. iii. 1955 (1955/46), five females with four males copulating and one free male.

Neoascaris mackerrasae from the small intestine of the Australian allied rat (Rattus assimilis) is described. It is compared with Neoascaris vitulorum and found to differ as follows:

(1) It is a considerably smaller species.

(2) The vulva is situated more posteriorly.

(3) The nucleus of the dorsal oesophageal gland is oval and situated in the dorsal sector of the ventriculus, whereas in N. vitulorum it is elongate and is situated in the sub ventral sectors.

(4) The eggs are more coarsely pitted.

(5) The spicules have two flanges which form a gutter on the ventral surface, whereas in N. vitulorum they are almost cylindrical.

The genus Neoascaris is redefined so as to include the presence of rudimentary cervical alae and the unequal distribution of the oesophageal glands. The genus is placed in the family Toxocaridae Hartwich, 1954.

Other ascaridoid parasites occurring in rodents are listed and differentiated from N. mackerrasae. It is suggested that on account of the arrangement in the ventriculus of the nuclei of the oesophageal glands, N. mackerrasae may represent a primitive species among the ascaridoid parasites of mammals.

(a) Glossina morsitans

1. A method of maintaining a breeding colony is described. The flies were best kept singly in tubes.

2. The optimum temperature and humidity ranges were 74–80° F. and 60–75% R.H., respectively. Young flies failed to tolerate a lower minimum temperature.

3. A light intensity of at least one foot-candle was needed at the feeding site.

4. The method of feeding the flies was of prime importance. Best results were obtained by offering food every fourth day, at a temperature of 80–81° F. The best feeding animal was sheep, but guinea-pig was useful for inducing newly emerged flies to feed. The condition of the skin at the feeding site was important, and it is suggested that frequently changing the feeding animal will lead to better feeding.

5. Female flies lived longer than male flies, and in both sexes the highest mortality was during the first 20 days of life.

6. The optimum age for mating was 10–14 days for males and 3–4 days for females; 90–100% of the first and second generation females were fully inseminated.

7. Each generation was less virile than the preceding one. Pupa production was decreased and the abortion rate increased from each generation to the next. Pupal viability, however, remained constant throughout all generations but the mean pupal weight showed a progressive decrease, except for the pupae from the second and third generation flies.

8. The mean interval without food during an interlarval period did not affect the duration of the period.

9. Feeding on the day of parturition did not significantly affect the length of the succeeding interlarval period.

10. The duration of an interlarval period was directly correlated with the length of the maximum interval without food during the period.

(b) Glossina austeni

11. A colony was maintained in a manner similar to that used for G. morsitans, but best results were obtained at 80–85° F. and 77–82% R.H.

12. Feeding was more satisfactory than in G. morsitans.

13. In longevity and reproduction the flies were superior to G. morsitans.

A study of neutralization reaction of trypanosomes with immune sera made against them is recorded, together with a description of the technique.

Neutralizing antibody appears in rabbits infected with T. brucei 5 days after infection and reaches its peak (1/320) within 28 days.

The same titre of neutralizing antibody can be produced in rabbits by a series of injections of dead formalized trypanosomes.

Antibody titres persist at high levels for a longer period in animals infected and subsequently treated than in animals immunized with dead trypanosomes.

Neutralizing antibody can be demonstrated in infected guinea-pigs but on a much lower level than in rabbits. Mice and rats infected with T. brucei and not treated failed to show demonstrable neutralizing antibody.

Mice infected with T. brucei can be protected from infection by inoculation at the same time, or even 1 hr. later, with 0·5 ml. of antiserum showing a high level of neutralizing antibody.

Mice inoculated with the same antiserum showed passive immunity lasting for 10 days.

The evidence that T. brucei ‘O‘ after passages through rabbits failed to be neutralized by homologous or heterologous sera which, on the other hand, were able to neutralize the parent strain, suggests that strains after passage through rabbits were not genetic variants, but developed a protective mechanism against immune bodies.

Agglutination reactions between living trypanosomes and sera of experimentally infected rabbits is described.

Agglutinins in infected rabbits and in hyperimmunized rabbits with dead trypanosomes appeared between 5 and 8 days and reached their maximum within 14 days. They persisted in infected untreated rabbits until death, but in infected rabbits treated with Suramin they persisted for only 3 months. In hyperimmunized rabbits the titre of agglutinins gradually fell and disappeared 4 weeks after the last inoculation.

Agglutinins appear to be species specific; sera of rabbits infected with T. brucei agglutinated homologous and heterologous strains of the T. brucei, but failed to agglutinate heterologous species of trypanosomes. Similar results were obtained with sera of other species of trypanosomes.

Four sera from naturally occurring cases of T. rhodesiense infection in man produced agglutination reactions with titre varying from 1:80 to 1:1280 with T. rhodesiense, but did not agglutinate T. brucei.

1. Metacercariae are recorded from the kidney tissues of slugs. Over 3000 slugs belonging to ten species were examined. Infection was confined to Milax sowerbii (Férussac) and Agriolimax reticulatus (Müller) apart from a few infected specimens of Arion ater (Linnaeus) or A. lusitanicus Mabille. Only one sporocyst was discovered and this occurred in A. lusitanicus.

2. Four distinct stages in metacercarial development are described—the caudal stage (0·7 × 0·3 mm.), the feeding stage (0·9 × 0·5 mm.), the corrugated stage (1·3 × 0·7 mm.) and the mature metacercaria (2·5 × 1·0 mm.). The corrugated stage is so-named because of the distinctive appearance of its cuticle.

3. Both the cercaria and metacercaria belong to the genus Brachylaemus (Dujardin, 1843) Blanchard 1847 and they probably belong to the same species. Since the life history is not known, no trivial name has been given to the organism.

The results of the examination of 543 faecal specimens by the Merthiolate Iodine Formaldehyde Concentration (M.I.F.C.) technique, Willis's salt flotation method and by direct saline smear are given.

The appearances of helminth ova and protozoan parasites in M.I.F.C. preparation are described.

The M.I.F.C. method showed a much greater efficiency for the detection of helminth ova over the other two methods. It did not prove as satisfactory for the detection of protozoan parasites. Effective concentration of trophozoite forms was not observed. The possible reasons for this are discussed.

It is proposed to adopt this method in combination with the direct saline smear for routine use in this laboratory.

Although the biological control of medically important snails has been suggested from time to time during the past quarter of a century (Nagano, 1927; Bequaert, 1928; Mozely, 1939, 1951; McMullen, 1952), the subject has, as yet, received but little serious consideration. Upon the initiation of our studies (Chernin, Michelson & Augustine, 1956a, b) the literature was searched for references to predators, parasites and diseases of molluscs which might furnish leads for experimental investigation.

The ability of certain species of trypanosomes (T. lewisi and T. equiperdum) to ingest previously stained oil drops which occurred simultaneously in the blood has been observed.

Tryparsamide incorporated in dyed (Sudan IV) cod-liver oil.when administered orally, was found to be effective against T. equiperdum infections in mice.

A score of these large amphistomes were found in the collection made by Dr P. L. LeRoux, to whom we wish to express our gratitude for the privilege of examining them, and to Professor J. J. C. Buckley for his interest in the work. The characteristically large posterior sucker and its muscular structure places this amphistome in Nasmark's Gigantocotyle.

1. P. tularensis may be abundant in the midgut lumen, the epithelial cells of the anterior third of the midgut, and the haemolymph of the louse. Multiplication is extracellular in the lumen and the haemolymph and intracytoplasmic in the gut cells.

2. The multiplication of the tularemia organisms in the midgut epithelium eventually leads to the disruption of these cells and the break-through of the organisms into the body cavity. The growth of these organisms in the haemocoele results in the death of the louse in 4–7 days.

3. Lice vary greatly in their susceptibility to infection. Some lice show complete resistance to infection; others are capable of retaining the infection essentially for their normal life span, i.e. 35 days; still others apparently succumb to a rapid increase of the organisms in a relatively brief time after infection.

4. The behaviour of P. tularensis within the louse presents interesting similarities to infection of lice with the rickettsiae pathogenic to humans.

Copepods belonging to the genus Lamippe live in the gastrovascular cavity of several alcyonarian genera. Eighteen species of these copepods are known (Zulueta, 1911), nineteen if the variety L. rubra decolor Zulueta 1908 is raised to species rank as suggested by Heegaard (1949). Each species is highly preferential in its choice of a host. Only one species is known to parasitize more than a single species of coelenterate, namely L. rubicunda (Olsson, 1869) which lives in two species of Alcyonium.

1. Psilochasmus agilis Travassos, 1921, is regarded as synonym to P. oxyurus Lühe, 1909.

2. P. indicus sp.n. has been described.

3. An amended specific diagnosis of Psilochasmus oxyurus has been given.

4. Ruddy Shelduck or Brahminy duck, Tadorna ferruginea (= Casarca rutila) is recorded as a new host of the genus.

Only 10 species of Nycteribiidae have been recorded previously from the Ethiopian Region and 3 further species from Madagascar. The writer recently described the new genus Dipseliopoda with three species, a new species of Eucampsipoda from Africa and another from Madagascar, (Theodor, 1955), 3 new species of Basilia and a new species of Tripselia from Africa (Theodor, 1956).

1. This paper reviews the morphology, distribution and hosts of I. schillingsi Neumann, 1901.

2. Two new species, I. rageaui from the Cameroons, and I. lemuris from Madagascar are described and figured. The latter shows obvious African affinities and is but slightly different from its African relative.

3. I. schillingsi is, with the exception of Lophiomys ibeanus (crested rat), known only from Colobus monkeys, I. rageaui from monkeys of the Cercopithecus group and I. lemuris from Lemur rufifrons.