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.

Patrick Alfred Buxton was born in Hyde Park Street, Paddington, on 24 March 1892, and died at his home in Gerrards Cross, Bucks, on 13 December 1955. His father was Alfred Fowell Buxton, a busy banker and one time chairman of the London County Council, his mother was Violet Jex-Blake.

A general morphological account of Multiceps smythi n.sp. from the local dogs in Dublin is given. This new species is characterized by forty-four rostellar hooks arranged in two rows of alternating crowns. Testes 286–310 in a single segment, occupying all parts of the segment in between the longitudinal excretory vessels, except the poral, posterior portion of the segment. Vagina opening posterior to the cirrus sac. Receptaculum seminis present. Uterus with 16–19 lateral branches on each side. Onchosphere enclosed in an embryophore, which is itself enclosed in a thin-walled capsule which has a bulge on one side containing fatty globules. The histological structure of Mehlis' gland and of the vitelline glands is also described.

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.

1. The morphology and histochemistry of the genitalia concerned in the formation of the egg in Multiceps smyihi n.sp. are described.

2. The vitelline cells are devoid of the phenolic protein globules, which occur in the vitelline cells of the Pseudophyllidea; this result is correlated with the absence of a true external egg-shell.

3. The hardened embryophore (often mistakenly termed the egg-shell) gives none of the reactions of sclerotin (tanned protein) or chitin, but gives a strong P.F.A.S. reaction for disulphide bonds, suggesting that it is a ‘keratin’ type of protein.

4. The cells of Mehlis' gland secrete a material which is intensely P.A.S.-positive and is not digested by saliva, α-amylase or hyaluronidase. This suggests that it may be secreting a mucopolysaccharide or muco- or glycoprotein.

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 manner by which Kuhnia scombri (Kuhn, 1829) Sproston, 1945, attaches itself to the gills of Scomber scombrus L. is described.

The parasite lies between the primary gill lamellae with its posterior attachment organs ‘upstream’ with respect to the gill ventilating current of the host.

The adhesive mechanism consists of two sets of organs which become attached to the secondary lamellae: a pair of hooks, provided with powerful muscles, perforates three or four secondary lamellae; and each of the members of four pairs of hinged clamps, operated by its own extrinsic muscle, grasps one or two secondary lamellae.

The description of the adhesive mechanism given differs substantially from that given by Sproston. Sproston's classification of the Diclidophoroidea, being based mainly on her interpretation of the structure of the clamps of Kuhnia, is therefore open to criticism.

During an examination of fishes for the parasitic crustaceans, fourteen specimens of Argulus belonging to two different species, viz. A. indicus Weber, 1892 (eight specimens) and A. siamensis Wilson, 1926 (six specimens) were collected from the fish, Ophiocephalus marulius Hamilton, taken from a canal in the environs of the village Champahati, District 24 Parganas, West Bengal. Out of seven fishes so obtained only three were found to be infected with the copepod parasites. While examining these copepods, the attention of the writer was drawn to a viviparous monogenetic trematode infecting only one species of Argulus, viz. A. indicus. It was rather unfortunate that the piscine host could not be examined at that stage for the helminthic infection. About one hundred specimens of this trematode were collected from the ventral surfaces of the copepods.

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.

The validity of the subgenus Hyalommina is discussed and reaffirmed.

Hyalommina is differentiated from Hyalomma by the absence of the subanal plates in the males and by the humped tarsi and the more or less hexagonal basis capituli in both sexes.

The male and the female of H. rhipicephaloides Neumann, 1901 are re-described. The larva and nymph of H. rhipicepholoides are described for the first time.

The Indian species H. hussaini Sharif, 1928 and H. kumari Sharif, 1928 are re-described. H. hussaini var. brevipunctata Sharif, 1928 is considered as a species inquirenda.

H. lewisi Schulze, 1936 is synonymized with Hyalomma truncatum K., 1844 (Feldman-Muhsam, 1954).

Three species of the genus Nematodirus have been described from sheep in Britain: N. spathiger, N. filicollis and N. battus.

The infective larva of N. spathiger has been described by Monnig (1931), and in more detail by Dikmans & Andrews (1933). The infective larva of N. filicollis was described and figured by Boulenger (1915). A brief description was also given by Morgan (1930), while Maupas & Seurat (1913) figured the larva but gave no description or measurements. In the present paper, the infective larva of N. battus is described and compared with those of the other two species. However, as in the course of this study certain discrepancies were observed in the published description of the larva of N. filicollis, a redescription of the larva of this species is also given.

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.

Toxoplasma ‘Nicolle et Manceaux’ has been examined in the electron microscope in thin sections of infected tissue cultures. The intracellular forms, single or in rosette formations, show that the parasite has no flagella, cilia or other organelles for locomotion. It is covered by a double membrane which is especially well denned at the two poles. A ring-like formation, often slightly protruding, can be seen at one end of the parasite, and in connexion with this, long, homogeneous, dark-stained inclusions of still unknown nature. At the opposite pole a distinct opening has been found.

Mitochondria and strands of an endoplasmic reticulum are also present in the cytoplasm and a fine striation in the region of the periplast. No dividing forms have been observed. Near the nucleus, in the region of what may correspond to the centrosome and the Golgi apparatus, a few extremely fine granules and a spiral-like formation of fine striae or tubules have been observed.

This work has been partly supported by the National Research Council of Brazil. The cost of reproduction of figures was defrayed by the Institute de Biofísica da Universidade do Brasil.

(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.

1. The phosphatases present in the adult and cysticercus stages of Taenia pisiformis have been investigated using histochemical and biochemical methods.

2. Histochemical tests failed to demonstrate the sites of enzyme activity in the cysticercus.

3. In the adult, the acid phosphatase is confined to the cuticle. Alkaline phosphatase occurs in the cuticle, subcuticular cells and the membranes bounding the ovary and vitelline tubules.

4. The histochemical distribution is uneven along the length of the worm, both acid and alkaline phosphatase being predominant hi the region of ‘mature’ proglottides. The scolex was negative to both tests.

5. Biochemical tests have demonstrated distinct acid and alkaline phosphatases in the cysticercus and adult stages. In the cysticercus the acid enzyme is predominant and in the adult it is the alkaline, implying a change in relative magnitude during the completion of the life cycle.

6. pH-activity curves have been obtained for the enzymes of both stages.

7. The results are discussed in relation to recent findings in the field of cestode enzymology, and it is suggested that these phosphatases may be associated with active transport of materials across the cuticle and ovarian and vitelline membranes.

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. Histochemical and biochemical studies have demonstrated the presence and distribution of phosphatases in Cysticercus tenuicollis and adult Moniezia expansa.

2. Biochemical tests have differentiated the following types of optimum phosphatase activity: Cysticercus tenuicollis, acid phosphatase, pH 5·0 (approx.); alkaline phosphatase, pH 10·0 (approx.); Moniezia expansa, acid plaosphatase, pH 5·5 (approx.); alkaline phosphatase, pH 7·0–8·0 and pH 10·0–11·0.

3. Attempts to locate the enzymes by normal histochemical methods were unsuccessful in the case of Cysticercus tenuicollis. In adult Moniezia, acid and alkaline phosphatase (both types) occurred in the cuticle. Alkaline phosphatase (pH 10·0–11·0) only was present in the tunicae enclosing the ovary, vitelline gland and testes. This enzyme was also the only one present in the interproglottidal glands, in the wall of the developing uterus and in the subcuticular cells.

4. Tests for all types of phosphatase activity showed that cuticular activity in Moniezia originated in the walls of an extensive branched system of channels. This system was demonstrable in the cuticle of fixed and unfixed material.

5. Incubation experiments with entire living Moniezia showed that substrates external to the body were capable of being broken down. Similar tests with Cysticercus tenuicollis showed that at least some of the alkaline phosphatase activity recorded by the biochemical tests was located in the cuticle.