An investigation of the factors necessary in the development of eggs of the mouse pinworm, A. tetraptera, outside the host, have shown that both oxygen and a suitable temperature (20–30°C.) are necessary. Development at high temperatures (37°C.) leads to a reduction in the number of infective eggs. It has also been demonstrated that there exists in the development of the infective eggs, a period of incubation during which the infective larvae within the eggs, though morphologically well-developed, are incapable of hatching.

A re-examination of the life-cycle of the mouse pinworm, Aspiculuris tetraptera has shown that the infective eggs hatch in the lower intestine or in the caecum of the host, to release the first stage larvae. After moulting, these larvae migrate into the crypts of the colon; those larvae which do not migrate into the crypts apparently pass out of the host with the faeces. The larvae in the crypts, presumably the third stage, later return to the lumen of the colon where they mature into adults. Males are mature by about the 20th day and females by the 23rd day. Viable eggs are released by the females 24 days after infection.

Parasites in the alimentary canal of 123 birds from the Wildfowl Trust collection at Slimbridge, Gloucestershire, are listed. About ten thousand helminths belonging to 26 species were found. The nematodes Hystrichis tricolor and Porrocaecum crassum and the cestode Nematoparataenia southwelli are reported from Great Britain for the first time, and a large number of new host records are given.

Twenty species of helminth parasites were found in the alimentary canal of thirty mallard caught in the decoy at Slimbridge.

The worm burden in grazing ewes was studied. Analysis of the results showed that correcting worm egg counts (e.p.g. fresh faeces) for variations in faecal D.M. content and in total faeces output is not of any great benefit unless precise information is available.

Data are also presented which suggest that under normal circumstances variations in the sub-clinical worm burden of adult grazing ewes are not related to any variations in food intake.

It has been shown that mice became infected after suckling from a female which has migrating Trichinella spiralis larvae within her body. The infections are usually of a very low order indicating that adult worms are not being picked up from the mother's faeces but that the infection is probably through the milk. It is also concluded that pre-natal infection of mice with T. spiralis occurs only rarely, if at all.

In two previous papers (Dissanaike et al., 1957a and 1957b) we described the technique of tagging Culex fatigans and Armigeres subalbatus (=obturbans) with P32 to obtain high beta activities. Filarial larvae were made to develop to the infective stage in these activated mosquitoes and were found to have beta activities high enough for detection individually.

By combining a number of well-known but scattered results, a theoretical model has been constructed to explain the observed quadratic increase in sample variance of egg counts over sample mean with increasing egg concentration. Our contention is that the over-dispersion arises because of inherent variation in volumetric deliveries of faecal suspension onto the counting slide. Even though the observed variation of volumetric deliveries appears to be small, we have shown that it is adequate to cause a considerable increase in egg count variance over mean at not unreasonably high concentrations.

(1) Cultures of Panagrellus redivivus increased and decreased in acidity as population increased and decreased.

(2) Comparison of the sex ratio of the mature worms present in the culture medium and, at the same time, on the walls and lids of the culture vessels, indicated a shift towards maleness in the sex ratio with distance from the culture medium.

(3) The results are discussed in relation to migratory behaviour.

The paper summarises the cases of cysticercosis on record at the Central Histology Laboratory, Salisbury, and describes two unusual cases of cysticercosis recently found.

1. The intake of microfilariae of Onchocerca volvulus in two series of females of Simulium damnosum fed on an infected human volunteer in West Africa and dissected after staining in London was from 0–171 microfilariae per female in one series and from 0–152 microfilariae per female in the other series. The distribution of microfilariae per female became more normal when plotted on a geometric scale.

2. The migration of the microfilariae was followed in the two series of flies by comparing the geometric (Williams) mean numbers of microfilariae in the stomach, abdomen, thorax and head, from 2 minutes to 48 houis after engorgement on blood. Microfilariae left the blood meal rapidly after engorgement, 40–50% leaving the stomach within the first 60 minutes.

1. There is a slow but definite loss of infective forms of B. pahangi from A. togoi maintained on honey and water alone and denied access to a host.

2. During the first blood meal after maturation of the filarial larvae there is a highly significant loss of infective forms from the mosquitos. On the 13th day, when they concentrate in the head of the mosquito, there is an unusually high (96·2%) loss after bloodfeeding.

3. The infective larvae migrate to and from the head and proboscis, and the thorax. There is also a migration to and from the head and the proboscis. This shows itself as a rhythm with 8 day oscillations.

1. Maritrema apodemicum sp. nov. from the long tailed field mouse, Apodemus sylvaticus sylvalicus (L.) on Skomer Island is described and compared with other species of the genus.

2. 14·6% of the mice were infested, the % infestation being greater in the males, 20·3%, than the females, 5·4%.

3. A brief discussion of the genus and of other species occurring in mammals is included.

A biological test to estimate the numbers of infective metacercariae of F. hepatica on pastures is described. The test is shown to be successful provided a snail site can be determined. Results from samples collected from field outbreaks are described and the possible applications of the test are discussed.

1. Biomphalaria p. nairobiensis, B. p. ruppelli and B. s. tanganyicensis have been found to be moderately susceptible to S. rodhaini from Kenya. A. glabratus from Puerto Rico is partially susceptible to the parasite. However, B. s. sudanica, B. dlexandrina, A. glabratus (Puerto Rico, albino strain) are refractory to infection with the same parasite from Kenya.

2. The present results together with those of some previous investigators suggest the existence of geographical strains of S. rodhaini.

The number of testes characteristic for males of Schistosoma mansoni has been described by various authors. Manson-Bahr & Fairley (1920) studying material from Egypt, reported that the males had 8 testes. Price (1929), Faust (1930), Neveu-Lemaire (1936) and Berghe (1939) reported that the number of testes varied from 8–9. Da Silva (1908), Lutz (1919) and Pinto & Almeida (1948) working on Brazilian material, gave the number of testes as 7, about 8 and C-9 respectively. Leiper (1918) studying material from Egypt reported that the number of testes varied from 7–9.

The ultrastructure of the metasomal body wall of the acanthocephalan Pomphorhynchus laevis has been studied.

The cuticle was seen to be pierced by numerous pores leading into tubular channels of the striped layer which appeared to have connections with the endoplasmic reticulum deeper in the body wall. The inner edge of the body wall was perforated by a number of channels which, it was thought, might form the final link in a chain of ramifying channels leading from the exterior of the parasite to the pseudocoel. The syncytial cytoplasm of the body wall was thought to be supported by the network of strands forming the felt layer.

Some years ago I suggested that a medical malacologist must not only learn to think like a population of snails but that he must also try to see those snails through the eye-spots of populations of trematode miracidia. For the past ten years I have been attempting to perform this unlikely combined feat. As time passes my tendency has been to concentrate on the second part of the contortion, partly because as a helminthologist it is natural to take a worm's-eye view of life and partly because it is very easy to become absorbed in the biology of the snails for their own sake. We should remember that if molluscs were not essential hosts to some parasites of man and domestic animals there would be no justification for a symposium on medical malacology.

p. 108—line 12 from top for “obnormal” read “abnormal”