1. Aedes togoi infected with B. pahangi were allo'ved to engorge on mice, to probe (but not to feed) on live and on dead mice, and to engorge on blood and on honey from cotton-wool pledgets. The number of worms in the mosquitoes after feeding or probing was compared with the number in unfed controls.

2. These experiments suggest that increased l?aemocoelic pressure as a result of the insect's gut filling with blood does not trigger the escape of nematodes from the mouthparts.

3. Host factors such as moisture, warmth, and chemical stimuli in the blood do not appear to be of any real significance.

4. The bending back of the labium, as the fascicle is driven into the skin, seems to be highly important. Some factor (or factors) associated with the movement of the mouthparts appears to be directly and chiefly responsible for the egress of infective filariae from the mouthparts of the mosquito blood-feeding on its host.

889 complete alimentary tracts were examined for helminths during a two-year survey of sheep and goats in Cyprus. Faecal samples were also examined for worm eggs.

The most common parasites found were Ostertagia and Trichostrongylus spp. and a list of all the parasites and their prevalence is given.

Bunostomum trigonoceplialum, Parabronema skrjabini and Skrjabinema ovis were found for the first time in Cyprus.

The infection rate of each of the worms was studied and the results showed that most of the worms followed the same general pattern, having a peak in the spring and another in the autumn, separated by a trough during the hot dry summer period, when the infection rate yvas low. There were variations within this pattern, Trichostrongylus spp. having a spring peak that was more pronounced than the autumn peak. The reverse occurred with Ostertagia, Chabertia and Oesophagostomum spp., which had a more pronounced autumn peak than spring peak and a lower rate of infection in the summer.

Variations in the infection rate were also noted between the two years of study.

The reasons for these variations are discussed and it appears that weather has some influence on the timing and duration of the peaks but that other factors must also be involved. It is suggested that with some species inhibition of development of the immature stages may occur over the hot dry period, and that these immature worms resume their development towards the end of summer.

A similarity was noticed between the seasonal distribution of the different worm species in Cyprus and in the winter rainfall areas of Australia.

The pathological effects of adult O. cervicalis on the ligamentum nuchae of infected horses are of minor importance and although small calcified or caseous nodules are sometimes found, chronic inflammatory conditions (poll-evil or fistulous withers) were not seen in the examination of over 120 infected horses. Pathological conditions due to microfilariae, in either the skin or the eyes of the host, were also of little importance and no reactions were seen which could definitely be attributed to the parasite. The only lesions seen on the abdominal skin of an infected horse, closely resembled the lesions of sweet itch which is not connected with the parasite but is probably due to a hypersensitivity reaction to the bites of the midge Culicoides pulicaris.

Microfilariae of Chandlerella hawkingi, a filarial parasite of the Indian jungle crow Corvus macrorhynchos Wagler, have been studied using the special staining techniques of Laurence and Simpson (1969). At the tip of the cephalic space a fang-like hook, bifurcated at the base, was visible. Near the hook four equilateral triangle-shaped spines could be seen arranged in a transverse row. There is a well defined oral ring. The pharyngeal thread starts as a funnel-shaped structure to end in the Innenkorper situated in the posterior third of the body.

889 alimentary tracts from sheep and goats were examined for worms during 1970 and 1971.

The severity of infection with each of the worm species is discussed and it is concluded that infections with Ostertagia spp. and Trichostrongylus spp. are the most important and that Haemonchus contortus, Bunostomum trigonocephalum and Chabertia ovina are of secondary importance.

The animals were divided into different age groups and a study was made of the severity of mixed infections in each group. The point system adopted by Parnell et al. (1954) was used for the study.

The most unexpected finding was that lambs and kids under 8 months old rarely suffered from infections of any significance. Infections built up slowly after that age. It was therefore presumed that animals remained vulnerable to infections at a much later age than in other countries.

Infections that might cause sub-clinical disease were seen in 31% of all animals and heavier infections were seen in 20% of the animals. This was considered a conservative estimate and shows the importance of gastro-intestinal parasites in sheep and goats in Cyprus.

Adult sheep appeared to be more heavily infected than goats, although some differences in animal husbandry between the two may have contributed to this.

From this study of age distribution, it was found that the autumn peak in the infection rate was not caused by the infection of young animals, which remained low at this time of the year.

The nature and histochemistry of the metacercarial cyst wall of five species of trematodes of different ecological habitats was investigated. Both structurally and chemically, the cysts of Posthodiplostomum sp. and Posthodiplostomoides leoncnsis are similar. They differ from the metacercarial cysts of Parorchis acanthus, Posthodiplostomum nanum and Clinostomum tilapiae

Observations have been made on the survival and migration of infective larvae of strongylid nematodes of the horse deposited on outdoor herbage plots. Few larvae ascended the herbage when conditions were very dry and migration was often enhanced by falls of rain. Larvae on the herbage died rapidly during summer but there was a much slower mortality rate during the winter months. An appreciable proportion of larvae placed on the plots in late summer and autumn survived until the spring but, at this time, there was a rapid disappearance of larvae which coincided with the rising temperatures.

The present paper describes the size range of Ternidens deminutus from human and baboon hosts in Rhodesia and discusses the possible reasons for the differences noted.

Using transmitted light and the scanning electron microscope, the external morphology of T. deminutus has been re-studied and compared to investigations by other authors using transmitted light microscopy alone.

The paper also illustrates the value of the scanning electron microscope in morphological studies in helminthology, especially when used in conjunction with the light microscope, to give an excellent three-dimensional picture of the species under investigation.

It is intended to follow this work with further studies on the anatomy, histology, ultrastructure and histochemistry of Ternidens deminutus.

A detailed description is given of a filarial parasite, Breinlia booliati sp. n. from the thoracic cavity of the Malayan rat, Rattus sabanus (Thos.) trapped in Malaysia.

Adult stages of Euclinostomum heterostomum (Rudolphi, 1809) were collected from the oral cavity and oesophagus of Bulbicus ibis in Liberia, West Africa. Structural relationships within the trematodes are clarified. A prepharynx from the oral sucker leads to a well developed pharynx to which the intestinal caeca communicate via a bulb-shaped oesophagus. The origin and extent of gonadal ducts are described including a Laurer's canal, whose aperture is dorsal. A discussion of the characters previously used to differentiate species of Euclinostomum corroborates the views expressed by Ukoli (1996) that the genus consists of two distinct species, E. heterostomum (Rudolphi, 1809) and E. multacaecum Tubangui and Maslungan, 1935. E. shrjabini Kurashvili, 1948 is proposed as a synonym of E. heterostomum. A compilation of the range in measurements of the adult and metacercarial stages of E. heterostomum is presented in the form of a table.

1. The number and duration of free-living and parasitic stages of N. dubius has been determined.

2. The results have been discussed in relation to previous accounts of the life cycle, and some of the discrepancies explained.

Four groups of 8 rabbits were infected with a range of doses of N. bath's larvae. The percentage recoveries of worms from groups receiving 100 and 1000 larvae were significantly greater than those from groups receiving 10000 and 50000 larvae. It is suggested that the worm population density is dependent on the degree of host response stimulated by the initial larval dose.

Experience of a chemically abbreviated patent infection of N. batlus gave significant protection to a group of 8 rabbits against establishment of worms from subsequent challenge compared with inexperienced controls.

Rabbits aged 5 months and 11 weeks were as susceptible to the establishment of worms as rabbits aged 7½ weeks; but age resistance vas manifested by the greater proportion of worms which developed to the fifth stage in the worm populations of the youngest group than in the other 2 groups.

The presence of Aspidogaster conchicola in the Netherlands has not been previously reported.

Regarding the relationship between the parasite and its host, the following observations have been made:

1. Infection of a new host with embryonated eggs of Aspidogaster conchicola gave positive results. A possible mode of infection via the nephridiopore is suggested.

2. The larvae apparently remain in the renal cavities of the host until they mature, when they move into the pericardium.

3. The larvae's development to maturity took at least three months at an average temperature of 18°C.

4. Visible damage to the host is confined to a deformation of the epithelium where the haptor (ventral sucker) is attached.

The phasmids of the first-stage larva of Dracunculus medinensis were paired, each consisting of a single cell with a lumen connected to the exterior by a closable duct. The cell consisted of an outer region filled with mitochondria and an inner region consisting of endoplasmic reticulum bordering the lumen, whose inner surfaces was supported by a fibrillar framework. There were a pair of cilia projecting into the lumen of each cell and two nerve bundles at the base in direct continuity with a branch of the lateral nerve. The lumen of the phasmidial cell contained acid mucopolysaccharides and esterases.

The dosing of rabbits with 300 000 or 500 000 larvae of Nematodirus battus produced. pathogenic effects in some rabbits similar to nematodiriasis in lambs. The clinical symptoms observed were diarrhoea, listlessness, anorexia and weight loss. Fourth-stage larvae were responsible for the onset of diarrhoea about one week after infection but immature fifth-stage worms and adult parasites may also have been pathogenic. Several of the clinically affected rabbits died, the others usually recovered during the fourth week of infection. There was no direct relationship between the occurrence of clinical symptoms and the size of the worm populations recovered at death or slaughter.

Comparison of two groups of weaned and unweaned rabbits showed that suckled rabbits were less susceptible to the establishment of N. battus infections and possibly to the effects of parasitism.

The development of the larvae of Breinlia booliati a new filarial parasite of the forest rat Rattus sabanus in Aedes togoi is described. Complete larval development to the infective stage occurred in the fat body of the head, the thorax, and especially the abdomen of the mosquito. The first moult occurs at 7 days and the second at 11 days. As the larvae grow very rapidly in length, the parts of the parasitized fat body cells which harbour the developing larvae take on a syncytial appearance. By the 11th day, the larvae move out from the fat body into the haemocoele. The infective forms are found in the proboscis at the 12th day after the infecting blood meal.

Brown and rainbow trout from Hanningf?eld Reservoir, Essex and rainbow trout from associated raceways were found to be infected with the metacercariae of Cotyluriis erraticus throughout 1968. Both o brown and rainbow trout of age 2+ introduced into the reservoir in the spring became heavily infected with C. erraticus during their first summer in the reservoir. Rainbow trout were more heavily infected than brown trout. Infection increased with age in rainbow trout but this was not apparent in brown trout. The metacercariae are almost completely restricted to the pericardial cavity of the trout. The life-cycle of C. erraticus in Hanningfield possibly involves gulls as final hosts and the gastropod Valvata piscinalis as first intermediate host. C. erraticus has probably been introduced into the reservoir in infected trout from outside sources, or by infected avian final hosts.

A study of the intestines of 208 carnivores (red fox, wolf and cat) from three different regions of Azerbaijan, Iran, revealed 10 species of cestodes: Taenia polyacantha, Taenia endothoracica, Echinococcus tnultilocularis, Joyeuxiella echinorhynchoides and Mesocestoides lineatus were found in Vulpes vulpes; Taenia multiceps, Taenia hydatigena, Echinococcus granulosus and Dipylidium caninum in Canis lupus; Taenia taeniaeformis in Felis sp.

Growth rate and activity of 10 nematode trapping fungi, (Hyphomycetes)—Arthrobotrys oligospora, Dactylaria brochopaga, D. gamsospora, D. polycephala, D. thaumasia, D. vermicola, Monacrosporium (Dactylella) bembicodes, M. {D.) cionopaga, M. {D.) ellipsospora, Trichothecium cystosporium—against the infective larvae of Ostertagia ostertagi and Trichostrongylus axei were studied. Species forming adhesive networks grew faster than the others. Species producing adhesive knobs, adhesive branches and constricting rings were, in general, slow growers.

Heterakis gallinarum known to transmit Histomonas meleagridis were transferred when 10 and 14 days old from chicken to chicken to chicken, chicken to chicken to turkey, and in other combinations of these 2 hosts. Results were compared throughout with those attending single transfers of worms and no transfer at all. H. meleagridis was liberated and became detectable in as little as 24 hours in some recipient birds. Recipient chickens some times developed infections with H. meleagridis even though the protozoan had never been found in either the original donors of 10-day larvae or donors of 14-day worms.

Recovery of mature Heterakis gallinarum from recipients of 10-day larvae was about 1 1/2 times that from birds in which heterakids developed from hatching to maturity without being disturbed. Transferred worms were 10–17% larger at maturity, suggesting that a single transfer at 10 days was less detrimental than uninterrupted development in the partially immunized bird. Recovery of H. gallinarum from turkey recipients of 10-day larvae equalled that from comparable chicken recipients, but turkey recipients of 14-day heterakids yielded fewer heterakids than did their chicken counterparts, whether 1 or 2 transfers had been made.