The morphology of Paramphistomum sukumum sp.nov. from Bos indicus in the Lake Region of Tanganyika, East Africa, is described and illustrated.

A list is given showing the incidence of nine species of the family Paramphistomatidae and three species of the family Gastrothylacidae found in cattle in the Sukumaland area of the Lake Region of Tanganyika.

In the present paper seven species of cymothoid isopods parasitic on the marine fishes of the Kerala coast are described. A preliminary diagnosis of three of them was published earlier (Pillai, 1954). Full descriptions of all the species are given below. The larval stages described were in all cases taken from the brood pouch. The present work forms part of a thesis for which the author was awarded the Ph.D. Degree by the Kerala University.

Factors governing the response of the Oriental rat flea, X. cheopis, to the white rat and to three murids were studied in an olfactometer.

Starved females aged 5–10 days were attracted to white rats, whereas starved younger females were repelled or indifferent. Starved males, 1–10 days old, were either indifferent or were repelled.

No clear-cut attraction of 7- and 8-day-old starved females towards the murids Meriones tristrami, Acomys dimidiatus and Microtus guentheri was observed.

Starved females increased their weight during the first 8 days of life by 12·0%, while starved males lost 2·2%. Females kept in a vessel with a white rat showed a 115·2% weight gain, while males under the same conditions gained only 18·8% (Table 5).

The authors wish to thank Dr F. G. A. M. Smit, of the British Museum (Natural History), Tring, Hertfordshire (England), for his valuable help in the preparation of the manuscript for this paper.

The genus Neoaplectana now contains eleven species of nematodes. All are associated with insects. A brief review of the history of the genus is given. An undescribed species referred to as DD-136 is compared with one other species in the genus Neoaplectana. It is very similar to the description given for N. carpocapsae Weiser, and it is concluded that it is probably this species.

The collection of large numbers of nematodes from Macropus rufus from Toganmain and Wilcannia in New South Wales and Cunnamulla in Queensland and from M. canguru from Cunnamulla has made possible the revision of five species and the description of three new species. The work is divided into two sections:

(1) Strongylina. Filarinema flagrifer Mönnig, Zoniolaimus setifer Cobb, Z. cobbi Kung, Rugopharynx australis (Mönnig) and Papillostrongylus labiatus Johnston & Mawson are re-described: Pharyngostrongylus alpha Johnston & Mawson and P. beta Johnston & Mawson are recognized as synonyms of R. australis; Filarinema moennigi sp.nov. is described from Macropus rufus.

(2) Oxyurina. Macropoxyuris longigularis gen.nov., sp.nov., and M. brevigularis gen.nov., sp.nov., are described from M. canguru. Re-examination of paratype material of oxyurids previously recorded from marsupials has made possible the presentation of more detailed descriptions, and the following nomenclatural changes become necessary: Oxyuris (s.l.) acuticaudata Johnston & Mawson is a synonym of Austroxyuris finlaysoni Johnston & Mawson: Syphacia trichosuri Johnston & Mawson is considered as Oxyuris (s.l.) trichosuri; two new genera are proposed, Potoroxyuris, for Oxyuris (s.l.) potoroo Johnston & Mawson, and Paraustroxyuris for Passalurus parvus Johnston & Mawson. Figures are given of Passalurus ambiguus (Duj.).

The material studied was made available by the generosity of Dr R. Mykytowycz of the C.S.I.R.O. Division of Wildlife Research, Canberra, to whom I am most grateful.

I am also indebted to Dr R. J. Ortlepp, Division of Veterinary Services, Onderstepoort, South Africa, for the gift of a sample of Rugopharynx australis, to Dr M. J. Mackerras, then of the Queensland Institute of Medical Research, for material from Macropus canguru from centres in south eastern Queensland, and to Dr G. B. Sharman of the C.S.I.R.O. Division of Wildlife Research for information on the correct names of the host species.

Nine hundred and five brown trout were collected from the River Teify, West Wales, over a period of 12 months and their helminth infestations are considered in relation to the age and sex of the host and season.

Only one statistically significant difference could be detected between levels of infestation in male and female trout of 1 and 2 years of age.

When trout of 3 years of age and over were spawning or recovering from the effects of spawning there is a tendency for sexually mature females to be more heavily infested with some parasites than the males. During the season of growth and maturation of the gonads this trend was reversed or became less marked. In the case of fish that were not spent or spawning the statistically significant differences showed the males to be more heavily infested than the females.

The possible reasons for these variations are discussed with particular reference to the roles of ‘physiological’ and ‘behavioural’ or ecological resistance'.

Observations are reported on the fluctuations in populations of gastro-intestinal nematode parasites in 68 calves on two dairy farms in Fiji based on fortnightly faecal worm egg counts over a 3-year period. On one of the farms the calves began to graze soon after birth; on the other farm they were reared indoors until they were weaned at 6 months of age.

The important species were Cooperia spp., Bunostomum phlebotomum, Haemonchus placei, H. similis and Oesophagostomum radiatum. Only small numbers of Trichostrongylus spp., Mecistocirrus digitatus and Neoascaris vitulorum were present.

Potentially pathogenic worm burdens were only found in young cattle, mostly between 2 and 15 months of age. Faecal egg counts for each parasite species rose independently to a peak and then declined to low levels. For most species there was a close relationship between the time at which the peak faecal egg count occurred and the age of calves on the same farm, irrespective of the season in which the calves began to graze. This is considered to be due to the high rainfall and constant high temperatures throughout the year resulting in at least minimal favourable conditions for the development and survival of the pre-parasitic stages of all species in all months of the year. It is concluded that the succession of species which occurred must be strongly influenced by intrinsic factors in the life-history of each parasite.

Tere were differences in the levels of peak egg counts between groups of calves which began to graze in different seasons but almost all parasite species examined were affected equally. The lowest levels were recorded in calves which were first exposed continuously to infection at the beginning of the dry season and the highest levels in those exposed at the beginning of the wet season.

Protection of calves from parasite infection, by indoor rearing until weaning at 6 months of age, did not confer any striking advantage as the acquisition of potentially pathogenic worm burdens was merely delayed.

The results are discussed in the light of recent theoretical concepts regarding the immunological control of helminth parasite infection.

I am indebted to Mr A. E. Harness of Wainivesi for permitting observations to be made on his dairy farm, to Deo Raj Singh and Ram Kumar for technical assistance, and to Dr D. F. Stewart and Dr J. K. Dineen of the McMaster Laboratory for their criticism of the manuscript. My thanks are due to Miss Suzanne Dodd and Mr I. T. Roper of the McMaster Laboratory for the preparation of the figures. The permission of the Director of Agriculture, Fiji, to publish this paper is gratefully acknowledged.

A method is described for obtaining sterile second-instar larvae of beet eelworm, Heterodera schachtii Schm., and culturing them to the adult stage on sterile excised roots of sugar beet, Beta vulgaris L. It was shown that beet eelworm is a primary pathogen, for sound uninjured radicles were invaded by larvae, and normal development of adult males and females followed. No females were fertilized, and no eggs were produced, which suggested that parthenogenesis cannot occur. Eelworm development stimulated the production of lateral roots. More adult females developed on radicles inoculated 24 hr. after excision than on radicles inoculated 72 hr. after excision, which may be related to the occurrence of maximum root extension during the first few days after excision. It is suggested that there are two parts in root tissue reactions: a thickening of cell walls as a wound reaction to mechanical injury, and formation of a syncytium in response to a chemical stimulus from the eelworm.

I thank my wife for assistance with this work, which was financed by the Sugar Beet Research and Education Committee.

The naturally oviposited egg of Dasymetra conferta is fully embryonated and it hatches only after it is ingested by the snail host, Physa spp.

Hatching appears to be in response to some stimulus supplied by the living snail. The stimulus causes the larva to exercise a characteristic series of body movements and to liberate a granular sustance (hatching enzyme) from the larger pair of its cephalic glands. This enzyme reacts with the vitelline fluid to create pressure within the egg capsule, and with the cementum of the operculum, so that it may be lifted away. The larva's escape from the shell, therefore, is due to a combination of pressure and body movements.

The hatched larva has a membranous body wall, supporting six epidermal plates, an apical papilla, two penetration glands and a central matrix (the presumptive brood mass).

It lives for about an hour within the snail and during this time there is a reorganization of the central matrix which terminates in the formation of an 8-nucleated syncytial brood mass.

The miracidial ‘case’, consisting of the body wall and the epidermal plates, ultimately ruptures to liberate the brood mass. Once the brood mass is free it penetrates through the gut wall in an incredibly short time.

Ciné film and direct observation showed that microphagous, plant and animal nematodes have the same basic wave pattern when moving. Their speed is linearly related to the product of their length and wave frequency during unrestricted movement in deep water. The speed, wave pattern and frequency of the plant nematode Ditylenchus dipsaci and the animal nematode Trichostrongylus colubriformis changed in a similar way in response to changes in water film thickness on the surface of agar of different concentrations. T. colubriformis like D. dipsaci were most mobile in a sand-water medium at a suction corresponding to the stage when most of the water has drained from the pores. The optimum temperature for activity of T. colubriformis and D. dipsaci was about 20° C. and both survived desiccation at 50% relative humidity and 24° C. for 32 days. T. colubriformis was attracted to and aggregated around grass roots (Phleum pratense). The results suggest that the free-living stages of microphagous, plant parasitic and animal parasitic nematodes move similarly and that nematodes can be divided arbitrarily into three groups: (1) those active enough to swim in deep water; (2) those able to swim in thick water films, escape from the soil and ascend plants above ground level; and (3) those too inactive to swim, the crawlers, which are largely confined to the soil. The habitat of free-living stages of nematodes, irrespective of their host or feeding habits, is probably related to their propulsive power.

We thank Dr D. Poynter for supplying the animal parasites used.

The muscular saucer-shaped haptor of the monogenean parasite Entobdella soleae is attached to the skin of its host Solea solea by means of a suction pressure generated within the sea-water-filled cavity enclosed between the cup-shaped haptor and the skin of the fish. The suction pressure is produced by the action of a pair of extrinsic muscles which are situated in the body of the parasite. Each extrinsic muscle communicates with the haptor by means of a long tendon which passes through a fair-lead in a prop-like accessory sclerite and is inserted on the end of a girder-like anterior hamulus embedded in the roof of the concavity of the haptor. The pull exerted by the muscles lifts the girders and the roof of the suction cup in which they are embedded relative to the props, thereby producing a suction pressure.

An electron microscope was used to investigate the ultrastructure of the tendon, which was found to consist largely of unbranched banded fibrils which differed from the collagen fibrils of vertebrate tendon in their diameter and periodicity.

I would like to express my thanks to Dr J. Llewellyn for suggesting the problem and for much helpful discussion. I am also grateful to Dr M. P. Osborne for tuition on the cutting of sections for electron microscopy. The work was conducted during the tenure of a Fishery Research Training Grant from the Development Commission.

Entobdella diadema produces spermatophores from a pair of follicular glands lying one on each side of the body alongside the main nerve cord, and the secretion of these glands is stored in a two-chambered reservoir within the cirrus-sac.

The vagina is made up of two regions, a wide distal part to receive, accommodate and digest the spermatophores, and a proximal narrow part connected through the vitelline reservoir with the oviduct.

E. diadema Monticelli, 1901, is shown to be distinct from E. bumpusii Linton, 1900, and has been recorded from two new hosts, Dasyatis pastinaca at Plymouth, and Myliobatis aquila at Naples.

We wish to thank the directors and staffs at the Plymouth Marine Laboratory and at the Stazione Zoologica, Naples, for providing excellent facilities for the above studies to be carried out. The work was assisted by a grant to one of us (J. L.) from the Trustees of the Browne Fund, to whom grateful acknowledgement is made.

Haematoloechus (Haematoloechus) exoterorchis sp.nov. and H. (H.) micrurus sp.nov. have been found in the lungs of Rana occipitalis (Gunther) in South Ghana.

62·5% of the frogs were infested with one or other or with both species.

The two species occupy different positions in the lungs of the host. H. (H.) exoterorchis is cylindrical and is wedged, anterior end foremost, into the alveoli. H. (H.) micrurus is flattened and remains free in the central lumen of the lung.

In the former case the wall of the alveolus, containing the worm, becomes stretched to a thin membrane.

The morphology of both species is described with reference to their different habitats.

A brief discussion of the genus is included.

I am most grateful to the University of Ghana and to the staff of the Zoology Department at Legon for the facilities which they placed at my disposal and without which the work could not have been done.

In three series of infections 32 mice were given metacercarial cysts of Fasciola hepatica X-irradiated at 3 Kr.: 8 mice received 20 cysts each and 10 mice 40 cysts each. In serial kills 9–24 days after infection 127 young flukes were recovered, 10 + 49 entire and 39 + 29 in serial sections of infected liver. These flukes were stunted and inhibited in their development. During a period of 8–22 days the length and breadth of the flukes increased from 0·53 mm. x 0·27 mm. to 1·12 mm. x 0·37 mm., whereas the mean length and breadth of normal flukes 22 days old is 3·4 mm. x 1·9 mm. The intestines of the flukes have about 10–14 lateral diverticula or sacculations but not normal branches during this period. In the sections of 12– to 29–day infections 16 dead flukes were observed in various stages of disintegration but flukes deemed alive at the time of fixation were noted in all stages from 8 days onwards, although some of them were injured by inflammatory processes set up in the liver. Injury is caused by massive infiltrations into the inner substance of the cuticle of band-type neutrophil leucocytes, which raise the epicuticle in extensive blister-like formations, but the basal portion of the cuticle (lamina vitrea) remains more or less intact. The cuticular sheets ultimately fragment, apparently as a result of chemical action, and leucocytes which had infiltrated into the cuticle rejoin the aggregate of similar cells inside the burrow. How the leucocytes effect an entry into the cuticle is not clear, but it is more probably by chemical than by physical means. When the epicuticle has been destroyed the fluke is in a dying condition. Few leucocytes penetrate into the parenchyma, suggesting that the lamina vitrea is relatively resistant to these cells and that death is due to chemical action following widespread but superficial damage to the cuticle.

The remaining 14 mice which received 40 X-irradiated cysts each were challenged 22 days later with 10 or 5 normal cysts. This procedure was followed by serial kills at intervals during the period 8–53 days after infection. Three almost mature flukes were recovered at 32 days and one mature fluke at 39 days. The mature fluke was of unusually small size (6·4 mm. x 4·3 mm.), but it had shed many viable eggs into the bile duct and gall bladder. The numbers of flukes of the challenge infections did not differ significantly from those of normal controls: 62 flukes in groups of 1–8 per mouse provided means of 4·4 flukes per mouse and 55·4 flukes per 100 cysts. In similar experimental infections of mice (which, however, received 2 doses of cysts X-irradiated at 4 Kr.) Hughes (1963) recovered 39 flukes in groups of 1–7 per mouse, providing means of 3·5 flukes per mouse and 35·3 flukes per 100 cysts. In his control experiments, which also serve as the writer's controls, 10 mice received 10 normal cysts each and in 22– to 29–day infections 34 flukes were recovered in groups of 3–5 per mouse, providing means of 4·25 flukes per mouse and 42·5 flukes per 100 cysts. There is therefore no evidence of immunity in terms of either delayed maturation or reduced fluke burdens. At all stages of infection flukes of the challenge infection bear comparison with flukes of single normal infections, except for an apparent diminution of growth (which requires confirmation) about 3–4 weeks after infection. This accords with generally accepted opinion that any small degree of immunity which is acquired by the hosts of liver flukes is almost undemonstrable. Further experiments with reduced periods between infections with X-irradiated cysts and a challenge infection may be profitable and are in progress but it is suggested that in such experiments nutritional effects may arise as a result of modification of the hepatic tissue on which young flukes feed by leucocytic infiltrations of the inflammatory reaction which is normally directed towards the repair of damage caused by the flukes.

My former pupil Denys H. Hughes, of the Parasitology Group, Allen and Hanburys (Ware), kindly set up the experimental mice to my specifications and I am deeply grateful to him for this kindness and consideration and for the respect he has shown for my wishes. Mice and cysts—X-irradiated as required— were supplied by Allen and Hanburys, for which my thanks are also proffered.

My personal technician, Mr John Wells, has attended to my technical needs constantly. In addition to making numerous series of excellent sections and whole mounts, he undertook the task of measuring several dimensions of more than 100 flukes. His patience and perseverance in the face of continual requests for more and more, good and still better materials has been commendable and I am glad to express my gratitude to him. I am grateful also to Mr R. D. Reed of this Department, who prepared the photomicrographs for Pls. 1–4 of this paper, sometimes when under the pressure of other duties.

Large numbers of Plagiorchis (M.) megalorchis Rees, 1952, were found in the small intestine of dying pheasant chicks in Peeblesshire, Scotland. This is the first record of this trematode in pheasants. In one chick one specimen of Brachylaemus fuscatus (Rud, 1819) was found, which is a new host record in this country. Unusual virulence of these trematodes in pheasants and turkeys is noted, showing lack of adaptation to these hosts. In addition to chironomids and midge, culicine larvae were infected with cercariae from naturally infected Lymnaea pereger. It is proposed to consider P. laricola Skrjabin as described and illustrated by Chertkova (1953) to be Plagiorchis bikhovskayae n.nom.

The author wishes to express his thanks to R. H. Duff, M.R.C.V.S., of the Ministry of Agriculture, Veterinary Laboratory, Lasswade, for placing the first pheasant chicks at his disposal, and to A. Howe, the gamekeeper at Holylee, for his information and willing help.

A description is given of a new species of notodelphyoid copepod which has been designated as Notopterophorus ionthus. It is parasitic or commensal in the branchial cavity of the tunicate Phallusia mamillata Cuvier.