The ultrastructure of the adult stage of T. colubriformis and H. placei was studied. The cuticle of both nematodes was composed of (1) a membrane-bound layer, (2) external cortex, (3) inner cortex, (4) matrix, (5)–(7) three fibre layers, and (8) a basal lamella. Pear-shaped bodies embedded in the matrix layer in H. placei occur, along the length of the animal, once per annulus. A thin hypodermis enlarged to form lateral, dorsal and ventral cords which contained hypodermal cells, nerves and excretory canals. The muscle cells were large and multilobular. Two sizes of myofilaments, present in the contractile part of the cell, conformed to the filament arrangement of obliquely striated muscle. The mouth, buccal cavity and oesophagus of the alimentary tract were lined with cuticle. The oesophagus contained gland cells, muscle cells and apical cells. The lumen of the intestinal cells of both species had a well-developed microvillar border. In H. placei each microvillus was encircled by a ring of apparently spirally orientated vesicles or tubules.

The authors are grateful to Dr D. W. Brocklesby for his help and advice. They would also like to thank Dr D. L. Lee and Dr W. G. MacMillan for helpful discussions.

An activity cell apparatus to facilitate quantitative measurements of motility of small nematodes in saline is described. The effects of salines with a pO2 either greater than 120 mmHg or less than 12 mmHg upon the motility of adult N. brasiliensis females was studied. The worms were found to require an oxygen tension greater than 12 mmHg to be able to maintain their motility.

I am grateful to Professors J. Brough and D. Bellamy for providing the facilities during the course of this study. I should also like to thank Dr R. A.Hammond for his supervision, help and criticism throughout the project, and Mr C. Welsby for his technical assistance in the construction of the activity cell.

This work was carried out during the tenure of a Scientific Research Council Studentship.

The fine structure of the shell formed round developing zygotes of an acanthocephalan has been described and compared with the descriptions from light microscopy. The origin of layer 1 from globules in the ovum has been postulated and a sequence of elaboration of the three shell layers has been suggested. The layers of the shell should continue to be numbered rather than labelled with descriptive terms until their origin and chemical composition have been established.

I should like to thank the Avon and Dorset River Authority for collection of the fish.

An extract of blood from Aotus monkeys infected with Plasmodium falciparum contained all the clones of malaria precipitins so far identified in human blood.

We are grateful to the Medical Research Council and Overseas Development Administration of Great Britain and to the World Health Organization for their financial assistance.

The course of single infections of Nematodirus battus was studied and the developmental phases of the fourth larval stage described. The third moult occurred between days 2 and 4 after infection and the fifth between days 8 and 10. The period of maximum larval penetration of the intestinal mucosa occurred around day 4 and most of the larvae had returned to the mucosal surface by day 6, during the middle of the fourth-stage. Some larvae remained deep in the mucosa and moulted to the fifth-stage in this site.

The relationship between growth and morphological development was not constant and was different in worm populations from different sites. Some larvae grew very rapidly during the early fourth-stage and then entered a period of lethargus while continuing to develop sexually, while others grew and developed throughout the larval stage.

The worms recovered from the second 30% of the small intestine were consistently smaller and less advanced morphologically than those from the first 30%. The worms in the posterior region of the small intestine were preferentially lost from the mucosa in the third- and fourth-stages between days 2 and 4 and from the mucosal surface as adults between days 12 and 16.

In rats treated with compound 48/80 or histamine, worm expulsion was inhibited. Treatment with a histidine decarboxylase inhibitor accelerated worm expulsion. Treatment with compound 48/80 elevates histamine and histidine decarboxylase levels and reduces circulating reagin titres. These results show that histamine is not responsible for worm expulsion.

Compounds such as isoprenaline and theophylline which increase cellular levels of cyclic 3′,5-AMP, prevented worm expulsion.

It is concluded that the evidence that amines are involved in worm expulsion needs reassessing and that cellular release mechanisms in general may be affected by drugs thought to act solely on amine release. In particular, the release of effector substances from sensitized lymphocytes on contact with antigen may be affected by these treatments.

The skilful technical assistance of Miss R. Keist and Miss I. Beeger is gratefully acknowledged. We thank Mr H. Berchtold, Biostatistisches Zentrum der Universität Zürich, for the statistical evaluation of the data.

Rats were infected with 1000 larvae at the time of mating and they were given a second infection while suckling a new-born litter some 3½ weeks later. Although they did have significantly more worms than immune controls such rats were nevertheless highly resistant to challenge with infective larvae. However, when challenged with adult worms, immunized lactating rats were unable to eliminate the second infection.

That the failure of self-cure in this case was not because adult worms are less antigenic in lactating rats was shown in the third experiment. Lactating rats were immunized by infection either with adult worms only or with larvae allowed to complete their life-cycle. When subsequently challenged with infective larvae during the same lactation, both groups were equally resistant. It is therefore concluded that in lactating rats the gut phase of N. brasiliensis infection is in some way protected from the self-cure mechanism. This may be due either to absence of an essential factor operating late in the process, or to the presence of a potentiating factor which allows the worms to survive.

The author would like to thank Professor W. I. B. Beveridge in whose Department this work was carried out, and the Agricultural Research Council for their financial assistance. It is also a pleasure to acknowledge the technical assistance of Mr J. A. Wilson and Mr P. W. Holmes.

Cordonema gen.nov. is proposed for C. venusta sp.nov. (type species), C. longifuniculata (Sobolev, 1952) comb.nov. and C. solonitzini (Sobolev, 1943) comb.nov. The genus differs from Skrjabinoclava Sobolev, 1943, in lacking laterally directed loops of the cordons. Cordonema venusta sp.nov. from Cinclus pallasi from Taiwan, differs from Cordonema longifuniculata in its spicule ratio of 4:1 compared to 2:1. It differs from C. solonitzini in having longer cordons in proportion to body size and in spicule ratio, which is 2:1 in C. solonitzini.

Skrjabinoclava cincli (Yamaguti, 1935) Sobolev, 1943, is redescribed from males and females from the type host, Cinclus pallasi, from Taiwan. Skrjabinoclava decorata (Solonitzin, 1928) Sobolev, 1943, is redescribed from Lonchura fuscans from Borneo.

Skrjabinoclava rallae sp.nov. from Rallus striatus from Palawan differs from S. horrida in its spicule ratio of 4.7:1 compared with 3.6–4:1, and in the structure of the right spicule. It differs from S. cincli in having shorter cordons and spicules. Skrjabinoclava amaurornae sp.nov. from Amaurornis phoenicurus from Palawan differs from S. alii Ali, 1968, in having longer cordons, shorter pharynx, and in the absence of a sclerotized bar connecting the first spines of the lateral rows. It differs from S. cincli in having larger body spines and a right spicule of different shape.

Keys to the genera in Echinuriinae and the species in Cordonema and Skrjabinovlava are included.

We wish to acknowledge the field support by Dr D. S. Rabor, Department of Biology, Silliman University, Dumaguete City, Negros Oriental, Republic of the Philippines, and the technicians of the Parasitology Department of Naval Medical Research Unit No. 2 for general assistance in procurement and examination of hosts. Dr John M. Kinsella kindly read the manuscript and improved it with his advice.

Young cercariae were covered with a thin nucleated primitive epithelium which was lost when the true tegument appeared beneath it. The tegument was at first similar to the primitive epithelium in that it was a nucleated, cytoplasmic syncytium but it could be distinguished from the primitive epithelium by its thickened outer membrane and by the layer of interstitial material beneath its basal membrane. The tegumental nuclei became pycnotic and disappeared and, at about the same time, nucleated subtegumental cells became continuous with the tegument. Two types of small, dense bodies were formed in the subtegumental cells and passed into the tegument. Later in development the tegument became filled with dense, granular material and spines were formed. The fully developed cercarial tegument was covered with a surface coat of fibrous material which was specifically attached to the outer membrane of the tegument.

The observations described in this paper formed part of a thesis approved by the University of London for the Degree of Ph.D.

The structure and ultrastructure of the excretory system of Panagrellus redivivus, Ditylenchus myceliophagus, D. dipsaci and the second-stage larvae of the Heterodera rostochiensis are described. Panagrellus has two lateral ducts, a median duct and a gland. The two lateral ducts are joined over the anterior part of the oesophageal bulb to form a loop. Anteriorly this loop continues as a median duct, which opens to the exterior in an excretory pit, part of the system lies free in the pseudocoelom. The lumen of the lateral excretory duct and the greater part of the median duct is surrounded by capitate tubules, which open into the lumen of the excretory duct. Capitate tubules develop by the invagination of the hypodermal membranes and lie embedded in thick cytoplasm surrounded by mitochondria. Ensheathed in cell membranes the excretory duct forms an anastomosis in the loop and at three other places along the length of each lateral excretory duct. At these regions there are nerve endings. The excretory gland opens posteriorly into the loop and is full of Golgi complexes, endoplasmic reticulum and secretory granules.

In the system of Ditylenchus and the second-stage larva of Heterodera the right lateral duct is absent while the left lateral excretory duct continues anteriorly past the median excretory duct; a true loop is not formed. The median excretory duct lies embedded almost throughout its length in the excretory gland. Capitate tubules are present along the length of the lateral excretory duct, but, unlike Panagrellus, are not present around the median excretory duct. Anastomosis is not formed in the excretory ducts. In other respects the system of the species studied is similar to that of Panagrellus.

The capitate tubules form a system of fine microtubules. Their ultrastructure and, particularly, their association with large numbers of mitochondria, is very reminiscent of structures thought to be concerned with an active transport role, related to ionic and osmoregulation in other phyla.

The excretory system is almost certainly hypodermal in origin. Differences between the morphology and relations of the median duct of Enoplus (Narang, 1970), on the one hand, and that of the other forms studied suggest that these ducts may have different origins: the presence of separate nuclei in the lateral duct and gland portions of the system would be consistent with this view. It is considered that the two parts may have originated separately and have become joined during evolution. It is also shown that the excretory system of Ditylenchus cannot be derived either from an H-shaped system or from a primitive gland system.

I wish to thank Professor C. Ellenby and Mr L. Smith for their helpful criticism.

Viktorocara acholonui sp.nov. is described from a babbler, Alcippe brunnea, from Taiwan. It differs from V. charadrii Belopolskaja, 1959, and V. guschanscoi Leonov, 1958, in having a longer pharynx and in shape of tip of left spicule, and from V. tenuis (Maplestone, 1932) in having 6 rather than 10–13 pairs of preanal papillae.

Smetaleksenema gen.nov. is proposed for Skrjabinobronema pileati Smetanina et Alekseev, 1968, which becomes Smetaleksenema pileati (Smetanina et Alekseev, 1968), comb.nov. It differs from Ancyracanthopsis Diesing, 1861, in having serrated cephalic processes. The species is redescribed.

Ornithostrongylus vetterlingi sp.nov. is described from emerald doves, Chalcophaps indica, from Borneo and Palawan. It differs from all other species in the shape of the gubernaculum and in possessing a striated, common spicule sheath which binds the spicules tightly together.

Also reported and briefly discussed are: Viguiera dicrurusi Gupta, 1960; V. buckleyi (Yeh, 1954) Chabaud, 1957; Cyrnea (P.) excisiformis Yamaguti, 1935; C. (P.) leptoptera (Rudolphi, 1819) Chabaud, 1958; C. (C.) eurycerca Seurat, 1914; Physaloptera alata Rudolphi, 1819; Ornithostrongylus quadriradiatus (Stevenson, 1904) Travassos, 1914; O. travassosi Maplestone, 1932; Amidostomum skrjabini Boulenger, 1926; and Epomidiostomum anatinum Skrjabin, 1915.

We wish to acknowledge the field support by Dr D. S. Rabor, Department of Biology, Silliman University, Dumaguete City, Negros Oriental, Republic of the Philippines, and the technicians of the Parasitology Department of Naval Medical Research Unit No. 2 for general assistance in procurement and examination of hosts, and to Mr H. G. Deignan (deceased), U.S. National Museum, for identification of birds.

Initial work for this study was supported by funding under Public Law 480, section 104(c), by funds provided by the Bureau of Medicine and Surgery, Navy Department Work Unit MR 005.20-0098, by contract no. NR 103-690/N 0014-66-C0094, between the Office of Naval Research, Department of the Navy, and the Southwest Foundation for Research and Education, and research grant HE-5-P01-6M-13252-02 from National Institutes of Health, USPHS.

Final efforts were sponsored by Department of the Army, contract no. DADA17-68-C-8094.

Upon stimulation, following a period of ambient conditions, infective A. tubaeforme larvae follow a committed characteristic pattern of activity, after being released by short-term mechanical or continuous photic stimulation. For the photic response this is stimulated by an increase in the intensity of stimulation, and for non-dark-adapted larvae a sudden fivefold increase in illumination is required, irrespective of previous stimulation.

Acetylcholine chloride, adenosine triphosphate, γ-amino butyric acid, histamine diphosphate, 5-hydroxytryptamine, neostigmine bromide, physostigmine (eserine), potassium hydroxide, succinyl choline chloride and d-tubocurarine chloride have been added to larvae and their subsequent postures and activity recorded. It is concluded that the typical activity pattern of larvae may be altered by the use of drugs which interfere with neuromuscular phenomena, and therefore the activity responses of infective A. tubaeforme are based on sensory and neurosecretory rather than energetic considerations.

We thank Mrs Helen Foreman for maintaining the larvae and the Medical Research Council of Great Britain for their generous support.

Twelve rabbits were dosed with infective larvae of a sheep parasite Nematodirus battus and killed in a serial manner over a period of 32 days. The percentage of worms which became established was 10–36% over the first 24 days after infection. The minimum period of development of the parasitic stages was similar to that in sheep, although adult worms recovered from rabbits were on average smaller than worms normally found in sheep. The course of migration followed by the parasitic larvae was the same as in sheep. The distribution of fourth-stage larvae and fifth-stage worms along the small intestine was that of a normal frequency distribution. N. battus was still infective for lambs and rabbits after one passage through the rabbit.

I would like to express my appreciation for the advice and encouragement given in the course of this work by Mr M. G. Christie.

Nippostrongylus brasiliensis of either sex, 216 h old, were injected directly in the intestinal lumen of 10-week-old laparotomized male rats in the duodenum or near the ileocaecal valve and their position ascertained 24 h later. Males migrated anteriad farther when females were placed in the duodenum than when they were alone or when 32P tagged males were in the duodenum. Females migrated anteriad similarly when they were alone or when males were in the duodenum or when 32 P tagged females were injected in the duodenum. The findings are consistent with the idea that females attract males anteriad at a distance.

It has been demonstrated that Hymenolepis microstoma in mice treated with cortisone grow larger than those in control mice.

The possibility of this being an immunosuppressive or growth-stimulating effect is discussed since the results from two strains of mice are different.

Antibody production is suppressed in the cortisone-treated animals and it is suggested that the circulating antibody normally affects a partial rejection of the worm.

I am grateful to Professor C. A. Hopkins and Dr T. S. C. Orr for many helpful comments during the course of this work and especially to Professor C. A. Hopkins for the facilities which he has placed at my disposal. Many thanks also to Miss Gillian Moore and Mr Jack Keys for their expert technical assistance. This work was in part supported by a grant from Fisons Pharmaceuticals Ltd.

In the winters of 1969 and 1970 a total of 64 rabbits was shot at 11 sites covering diverse climatic regions in the western, central and eastern districts of New South Wales. The ectoparasites of these rabbits were identified and counted. The flea Echidnophaga myrmecobii was most frequently found in western districts; the louse Haemadipsus ventricosus was prevalent in the central districts; the mite Listrophorus gibbus was very abundant on rabbits from the eastern districts, whilst the mite Cheyletiella parasitivorax was prevalent on rabbits from central and eastern districts.

The probable consequences of these variations are discussed in relation to their possible effects on the epidemiology of myxomatosis.

This investigation was carried out as part of the study of the biology of the wild rabbit undertaken by the Division of Wildlife Research, CSIRO, under the general supervision of Mr K. Myers. The author is indebted to P. Haycock and Miss S. Stephens for invaluable technical assistance. Messrs I. Parer, M. Stranger, G. Richards, H. Bults, J. Libke and P. Haycock shot the rabbit samples.

The writer (Sprent, 1971) described four female specimens of an ‘ascaridoid’ nematode from a vial labelled ‘Tasmanian Marsupial Wolf’. The name Cotylascaris thylacini was proposed, in spite of there being no male specimens available. This was because no other genus among ascaridoids was known by the writer to possess cup-like cuticular structures on the margins of the lips and also because the thylacine (Thylacinus cynocephalus) is considered to be on the verge of extinction, if not extinct already.

The transformation of cercariae of Schistosoma mansoni into schistosomula has previously been achieved by passage through membranes of biological origin. This transformation has now been effected in the absence of a membrane. Chemical stimulus for transformation results from contact with human or rat skin lipid and fractionation of the latter led to localization of the active component in a fraction containing phospholipids. The series of processes involved in transformation was subsequently found to be set in motion by the action of egg lecithin-water mixtures on an aqueous suspension of cercariae and yields of 90% of live schistosomula may be obtained reproducibly with crude egg lecithin-water in the ratio 1:50. The juvenile worms were found, by accepted criteria, to be identical to those produced by the normal penetration procedure. Purified lecithin does not produce the same stimulus and the effect of the physical state and of possible impurities present in crude egg lecithin is discussed.

This work was supported by the Conselho Nacional de Pesquisas (Brazil), the Banco Nacional de Desenvolvimento Econâmico FUNTEC contracts nos. 99 and 110 (Brazil), U.S. Army Grants nos. DAHC-19-70-G-0017 (to B.G.) and DAHC-19-70-G-0070 (to J.P.) and by the FORGE Foundation. Contribution no. 18 from the Schistosomiasis Research Unit, Institute of Biological Sciences, Federal University of Minas Gerais, Brazil.

This study examines the ultrastructure of the posterior vacuole in frozen-etched spores of Thelohania bracteata (Nosematidae), a microsporidian infecting the fat body of larval black-flies (Simuliidae). This organelle, considered important in providing intrasporal pressure for sporoplasm extrusion through the polar filament, has a double membrane with particles on its internal faces as revealed by the freeze-etching technique. The size and pattern of these particles differ from those in membranes of the polar filament and nucleus, and this difference may have functional significance. The posterior vacuole, and also the polaroplast, may originate from expanded sacs that occur in the immature spore. There is evidence from this study that there are many basic ultrastructural similarities between spores of different microsporidian species and that at least some reported differences are the result of varying techniques.

We gratefully acknowledge the freeze-etching facilities provided by the Department of Pathology, Faculty of Medicine, McMaster University. The research was supported by Grant A-130 from the National Research Council of Canada.

Biochemical studies on the non-specific phosphomonoesterases of Fasciola hepatica have shown the presence of acid phosphomonoesterase active at pH 4·6 and two forms of alkaline phosphomonoesterases active at pH 7·6 and pH 9·6 respectively. Histochemical studies have located acid phosphomonoesterase in the walls of the intestinal caeca and to a lesser extent in the tegument. Alkaline phosphomonoesterase was found to occur mainly in the excretory ducts and to a lesser degree in the uterine wall. Glycogen was mainly concentrated in the yolk glands, parenchyma, mature eggs and the non-muscular regions of both oral and ventral suckers.

Dr A. J. Probert takes pleasure in recording the support of the British Council and the Indian University Grants Commission to enable him to study in India.