A new halarachnid mite, Zumptiella coreaensis, is described from female and male specimens obtained from the nasal cavities of the Korean squirrel, Sciurus vulgaris coreae, collected from Korea. A key to the species of the genus Zumptiella is presented.

During the present century oogenesis and maturation have been extensively studied in the Digenea. The earlier observations, however, were based on limited methods of histological and cytological techniques and were concerned principally with the general features of the germ-cells and with their chromosomes. Consequently, until recently, little information has emerged regarding the extra-nuclear components of oogonia and oocytes and the changes that these cells undergo during oogenesis. The earlier work on the Digenea is reviewed by Cable (1931), Anderson (1935), Rees (1939), and more recent research is cited in the present paper.

1.Studies on the histological changes during digestion in Argas persicus reveal that the ingestion of blood is accompanied by the destruction of the existing gut epithelial cells.

2.The blood remains unlysed for 2–3 days while a new epithelium develops which contains cells that secrete a saliva-fast PAS-positive colloid that causes haemolysis.

3.Other epithelial cells remove the freed erythrocytic nuclei by phagocytosis.

4.Most of the gut cells then absorb protein from the lumen and intracellular digestion takes place leaving pure haematin granules as the waste product of the digestion of haemoglobin.

5.After the initial rapid phase of digestion only relatively few cells show signs of absorptive and digestive activity.

6.Absorption of protein is accompanied by increased alkaline phosphatase activity in the microvilli of the cell border; this activity is lost once absorption finishes and digestion begins.

7.Strong aminopeptidase activity can be demonstrated at the border of some of the protein vacuoles.

8.In vitro tests show that the gut proteinase is active only in the acid range with peaks at pH 2·6 and 3·8 and has a Km of 0·32 % with bovine serum albumin as substrate.

9.In vivo data show that digestion, after haemolysis has occurred, takes place in two phases; the first is rapid and lasts approximately 1–2 weeks and is followed by the second phase which is slow and remains constant until the next blood feed.

10.The proportion of the blood meal which remains after the rapid phase of digestion is determined by the sex and developmental stage of the tick and within each category it is constant and serves, in the absence of significant fat and glycogen reserves, as a food reserve.

1.The morphology of Protopolystoma xenopi from Uganda is compared with specimens previously described by Williams. The chief differences are the slightly greater maximum size, the presence of a second pair of anchors on the opisthaptor, and the absence of a second large oviducal chamber in the uterus.

2. Encapsulation of the egg is described from living worms. A thin, plastic membrane forms around the ovum and yolk cells within the ootype before all the yolk cells have passed into the ootype. The remaining yolk cells pass from the ovo-vitelline duct into the sac formed by this membrane, which is attached to the distal walls of the ootype.

3. Eggs are produced at the rate of 4–15 eggs/worm/24 hr. They hatch in 24–27 days at 24–26° C. The opisthaptor of the larva bears sixteen hooklets and two pairs of anchors, which are in the same positions as in the adult.

4. One larva with one pair of suckers was obtained from the alimentary canal or kidney of a metamorphosing Xenopus tadpole. About sixty other tadpoles were examined for P. xenopi but none was found.

5. Twelve P. xenopi were recovered from the kidneys of a small frog that had been infected experimentally 10 days previously.

6. When naturally infected small frogs from Kajansi Fish Farm were examined, immature P. xenopi were found in the kidney of one frog, in the urinary ducts of two frogs, and in the bladder of one frog. The infection rate was much lower than that in mature Xenopus. Immature P. xenopi were also found in the kidneys of mature Xenopus mülleri.

7. P. xenopi matures more rapidly than its host. A frog weighing only 2·9 g. contained a nearly mature worm in the bladder, while one weighing 4·2 g. contained two mature worms, shedding eggs. Eggs are shed throughout the year. The life cycle of P. xenopi is therefore not regulated by that of its host.

The Mochlus fernandi lizards (Scincidae) from the Kivu province (Congo) around Lwiro, Katana, are infected with a broad leaf-like monomorphic trypanosome, Trypanosoma mochli. The high moisture requirements of M. fernandi, which resemble European salamanders, and the morphological similarity of T. mochli to amphibian trypanosomes point to an aquatic transmission and vector for this species.

1. A detailed description, with illustrations, is given, of the sequences in development and maturation of the genitalia in Tetrabothrius erostris. This is the first such account of any member of the new order Tetrabothridea.

2. The effect of the very marked protandry on the form of the remainder of the genitalia is discussed.

3. Attention is drawn to the unusual ovary which produces sclerotin and which it is proposed to call a ‘calycal-ovarium’.

4. Comparison is made of the embryophore with that of the Cyclophyllidea. There is a suggestion that the embryophore may be formed of sclerotin in T. erostris.

5. Par-uterine vesicles have been described for the first time in any member of the Tetrabothridea. These vesicles arise from the uterine primordium and have previously been confused with testes.

6. The complex affinities of the order Tetrabothridea are discussed and some support arises for the creation of this new order.

1. The exrectory system of Anoplocephala perfoliata has been re-described and shown to consist of a dorsal ‘network’ system of vessels to which the flame cells are connected and a ventral pair of longitudinal vessels linked only by a transverse vessel in each proglottid.

2. The two excretory systems unite only in the apical ramifying vessels of the scolex.

3. Alkaline phosphatase activity was demonstrated in the cuticular microvilli, the subcuticular region and in the excretory vessels.

4. Non-specific esterase, insensitive to 10−4m E 600, was located in the lappets and embryonated eggs and esterases, inhibited by 10−4m E600, in parts of the cuticle and subcuticular region and parenchyma.

5. Cholinesterases were found in the nervous system and in the reproductive ducts.

6. Aminopeptidase was found in the neck region, in the undifferentiated proglottids, the active testes and ovaries, the male reproductive ducts and in the region of high metabolic activity in the fringe of the proglottid.

The perch was the principal host for the plerocercoid of Triaenophorus nodulosus in Llyn Tegid.

Three stages of plerocercoid development were recognized: non-encapsuled developing plerocercoids, encapsuled but living mature plerocercoids, and dead encapsuled degenerate plerocercoids.

The stomach contents of the perch were analysed and planktonic crustaceans were found to be a significant part of the food from May to December. No change in diet in relation to length was found.

The period of occurrence of developing plerocercoids in the perch livers was March to June. This in relation to other evidence was shown to indicate the period of infection of the perch by the procercoids.

The three stages of plerocercoid development recognized were found to occur simultaneously in a few perch, and thus may represent infections acquired over three successive seasons.

There was no seasonal periodicity of occurrence of the plerocercoids in the perch.

All the perch examined were more or less equally infected by plerocercoids. There was no tendency for older, longer perch to be more heavily infected.

One to five capsules, normally containing one plerocercoid each, occurred in the livers of the infected perch.

For the perch examined there was a dynamic equilibrium between establishment of procercoids from the copepod host, and loss of plerocercoids by degeneration within the perch.

The mature plerocercoids form the reservoir of infection for the definitive host of T. nodulosus, the pike.

Within recent years, problems of host-parasite relationships have been receiving increasing attention from parasitologists. This is particularly true in the study of the cestodes Echinococcus spp., where predilection for different hosts—when considered with the morphology of the adult and the growth and development of the larva—seemed sufficiently significant to lead to the establishment of the two species, E. granulosus and E. multilocularis. Much experimental and field work has been carried out on a variety of vertebrate hosts and a number of new, naturally infected and laboratory hosts have been reported. A survey of intermediate and definitive hosts has been undertaken in this laboratory as part of a study to investigate whether factors of morphological, physiological or biochemical origin were concerned in host specificity. These data, together with some genetical considerations, form the basis of the present paper.

1. The mode of attachment of Echinococcus granulosus to the dog intestine was examined.

2. In an attached worm, the scolex was found to penetrate deeply into the crypts of Lieberkühn, with the rostellum fully extended, the hooks penetrating the epithelium lightly and each sucker holding a ‘plug’ of mucous cells in its cavity.

3. The expansion of the rostellar tip was aided by a muscular disk, the rostellar pad, which probably assists attachment by forcing the hooks outwards.

4. The epithelium in the region of the suckers showed eosinophilic reactions which may indicate a mild host reaction.

5. The existence of a small group of spindle-shaped secretory cells which form a rostellar gland, lying immediately anterior to the rostellar pad, is reported. This gland was found to be the source of secretion droplets seen to be released in vitro from the scolex region.

6. The secretion droplets were found to be exceptionally labile and not preserved in the rostellar gland cells by routine fixation methods. Prolonged fixation (5–12 months) in formol (7% formaldehyde) gave excellent preservation but globules were fairly well preserved after 3 months fixation. Fixation in Baker's formol-calcium for 2 weeks followed by controlled chromation was also found to retain the secretion reasonably well but not as adequately as the prolonged fixation.

7. The secretion was found to be negative to the PAS, bromo-phenol blue (with Hg), and ninhydrin-Schiff reactions. The areas adjacent to the globules gave a protein reaction and the periphery of the globules appeared dark by phase contrast microscopy.

8. The secretion was weakly positive to performic acid-Schiff and gave strong reactions with Sudan Black after controlled chromation, both in frozen and wax sections. These results suggest that the secretion may be a liproprotein or a lipid-protein coacervate but it is recognized that confirmation by biochemical methods is desirable.

9. The possible immunological implications of these results are discussed.

This work was supported by the Australian Wool Research Committee and the U.S. Public Health Service Grant No. E. 4707–02. The technical assistance of Mrs A. L. Warrener and Mr A. B. Howkins is gratefully acknowledged.

The studies presented in this paper describe the effects of control exerted by the immunological response of the host (sheep) on the developmental stages and fecundity of the parasite Nematodirus spathiger. Thirty Merino lambs, maintained worm-free, were randomly divided among three treatment groups each containing ten animals. The group 1 lambs were each given a single dose of 50,000 infective larvae, the group 2 animals were given a single dose of 130,000 infective larvae, and the group 3 animals were given twenty-five consecutive daily doses of 2000 infective larvae. Group fecundity was estimated by performing worm egg counts on daily faecal samples and development of the parasite burden was followed by carrying out differential worm counts on animals slaughtered at crucial stages during the infections. Total fecundity was greatest in group 1 and least in group 3 with group 2 intermediate. An inverse relationship between total fecundity and percentage retardation of development (percentage of 4th-stage larvae in the total worm burden) was demonstrated between the three treatment groups.

The results of the studies also show that control of the parasitic infection is mediated about threshold levels of immunological responsiveness and is expressed by (1) elimination at the infective (L3) stage, (2) retardation of development at the L4 stage, (3) reduction in egg production of the adult female, (4) elimination of adult worms, and (5) discrimination against the female in both the degree of retardation in the L4 stage and the extent of elimination in the adult stage.

Great variation in response was observed between individuals within treatment groups. The source of variation is attributed to differences in degree of antigenic disparity of the parasite with individual members of the heterozygous host population in which antigenic characters are not uniformly segregated.

The concept of ‘fitness’ of the parasitic species was introduced into the discussion to provide a rational interpretation of the results.

We are indebted to Dr S. S. Y. Young, Division of Animal Genetics, C.S.I.R.O., for advice and assistance with the statistical analyses, which were performed by Mrs M. Tonkin, and to Dr D. F. Stewart for his constructive criticism of the manuscript. Careful technical assistance was given by Mr E. Teleki and Misses Helen Giller and Berenice Merchant.

A modification of the controlled test is described. This is designed to assess the value of a drug against immature as well as against the adult stages of the gastrointestinal nematodes of sheep. The use of faecal egg-count data in the assessment of anthelmintic activity is compared with the critical and controlled tests and the comparative value of all three types of test is discussed.

A simple but efficient apparatus for harvesting nematodes migrating from their insect hosts is described. Infected host larvae are supported, in contact with water, on a nematode-permeable diaphragm resting in the mouth of a large funnel. A battery of funnels can be connected in series and their water-level maintained by a common constant-level device.

1. The distribution of glycogen and lipids in three oxyuroids (Aspiculuris tetraptera, Enterobius vermicularis and Syphacia obvelata) is described and found to be similar to that in ascarids and other oxyuroids.

2. Evidence is presented for the presence of both polysaccharides (possibly glycogen) and lipids in the cuticle.

3. It is suggested that the chitinous layer of the egg-shell of A. tetraptera contains phospholipids in association with proteins.

4. The distribution of phospholipids is described and it is suggested that their role is mainly structural.

I am grateful to Dr P. Tate for advice and encouragement and to Dr D. L. Lee for much useful discussion and advice.

1. Four trematodes, Gastrothylax crumenifer, Cotylophoron cotylophorum, Paramphistomum explanatum and Fasciola gigantica have been used for quantitative analysis of their inorganic constituents.

2. Calcium, magnesium and phosphorus content have been determined.

3. All the four trematodes contain large amounts of phosphorus (0·61–1·05%); but the amounts of calcium (0·025–0·045%) and magnesium (0·029–0·065 %) are small.

Data on 279 species of trematodes of birds and mammals are analysed in tables, to show the molluscan orders and families that act as first intermediate hosts of various trematode families.

Host-specificity is highly developed in the first larvae of trematodes and it is suggested that, as a consequence of this, certain species, genera and families of molluscs harbour a greater variety of trematodes than others. The families Lymnaeidae, Physidae, Planorbidae, Hydrobiidae and Thiaridae are by far the most important first-intermediate hosts of the trematodes of birds and mammals whose life cycles are known; each family acting as host of not less than twenty-four species and eight families of trematodes.

This paper is published with the approval of the Director General of Health, Canberra, A.C.T.

Samples of the snail Velacumantus australis from an area of 10 yards in diameter, were examined to determine if the incidence of larval trematodes varied with the density of the snails. The incidence in susceptible snails from areas where the density was less than 20 snails/sq. ft. was found to be significantly greater than in snails from areas where the density was higher than this. Further analysis showed that the variation in incidence, with density, was due almost entirely to the juvenile part of the population.

Success in immunizing rabbits, rats and sheep with dead trypanosomes depends on the method of killing trypanosomes, the frequency of inoculations, and the strain used for immunization. Positive results were obtained when trypanosomes were killed by formalin or by freezing and thawing five times. Negative results were obtained when trypanosomes were killed by 56° C. for half an hour.

Animals which received 10 doses of the mixture produced better results than those which received the same amount but only in 2 doses. An addition of Freund's adjuvant improved results, but 10 doses without an adjuvant were still better than 2 doses with an adjuvant. When trypanosomes were killed by 0·5% formalin, only an M variant of T. brucei, which was maintained by frequent passage in mice and was an antibody-sensitive variant, was able to produce in animals protective antibodies and resistance to a homologous ‘M’ variant, but not to an ‘R’ variant. On the other hand, if an ‘R’ variant of the same strain, which was passaged forty-eight times through rabbits and became resistant to antibodies, was killed by 0·5 % formalin and inoculated into animals, no antibodies and resistance could be demonstrated to a homologous ‘R’ variant and an ‘M’ variant.

Although it is possible to produce immunity in animals with dead trypanosomes further studies, particularly in the field, are necessary to find its practical application.

Extensive cross-reactions have been found between cultural forms of trypanosomes of the ‘brucei’ group by the agglutination reaction. The antigen (or antigens) responsible for agglutination are apparently specific to the ‘brucei’ group of trypanosomes. These antigens are also quite stable to the presence of specific antiserum in contrast to the serotype of the blood trypanosomes which are known to be altered in the presence of specific antiserum.

Evidence is presented of a periodicity of oogenesis and spermatogenesis in D. aegira. Pauses in oogenesis were detected between successions of oogonial divisions; in spermatogenesis, the intervals appeared to be longer and the pauses came before division of primary spermatocytes. Regulation of division rates was such that between two and three times as many spermatozoa as oocytes were produced.

Observations indicated that spermatozoa emerged from the axial cell soon after their formation and made contact with oocytes early, often before these were fully grown. Properties of the oocyte cell membrane evidently precluded precocious sperm entry and the penetration of more than one spermatozoon.

Sincere thanks are due to Dr R. B. Short, who kindly made available all the material, and to Dr S. W. Fox and Dr C. B. Metz for the excellent facilities provided. This work was supported by P. H. S. Research Grant E 4749 (Institute of Allergy and Infectious Diseases) awarded to R. B. Short, and by N.A.S.A. Grant NsG–173–62 and N.S.F. Grant G–9150. Contribution No. 019 of the Institute for Space Biosciences.