The use of worm egg counts for observational and experimental purposes in naturally infested sheep has become very popular since Whitlock and Gordon (1989) introduced the simple and efficient McMaster slide technique. When using a dilution technique such as this, the accuracy of the count increases as more eggs are counted. In order to count more eggs when using the McMaster slide it is usually more convenient, in practice, to take more samples (i.e. count more cells) than to alter the dilution. It is therefore desirable to know the optimum number of samples which should be counted for each sheep when comparing the counts of naturally infested sheep. The usefulness of sampling on one or more days is another problem concerning experiments of this nature.

Research on the potato-root eelworm Heterodera rostochiensis has been severely handicapped by the fact that it is virtually impossible to estimate the infectivity of individual cysts. Since the infectivity of an individual cyst is determined by the number of viable larvae present within it, the problem can be settled in one of two ways—either by means of a technique which recovers all the viable larvae and rejects the non-viable or by estimating firstly the total contents and then the proportion of them which is viable. Techniques for the recovery of larvae from cysts have been described by Fenwick (1941) and Fenwick and Franklin (1940). The former of these sought to express soil infectivity directly in terms of available larvae per gm. of soil while the latter was concerned merely with obtaining a representative sample of larvae from a given batch of cysts. Neither claimed to estimate viability of the contents. A further technique (Bracey, 1946) which was described in a paper circulated among interested workers was a modification of that described by Fenwick and Franklin (loc. cit.) and claimed to express viability of cyst contents directly as a percentage.

Dr. J. P. Caplan (1949) of the Ministry of Pensions Tropical Diseases Unit, Queen Mary's Hospital, Roehampton, reported that in the course of 8 years he had observed several hundred cases of creeping eruption am, ong ex-prisoners-of-war from the Far East and that more than 98 per cent, of them had Strongyloides infection.

According to Napier (1949), who comments on this condition, at least 90 per cent, of these patients had worked in Siam on. the notorious railway. One of Napier's cases came from the Assam-Burma frontier and one of Caplan's from Java. Professor J. J. C. Buckley, who was consulted, was of the opinion that morphologically the parasite in the faeces of these patients was in no way different from S. stercoralis Bavay, 1876).

The writer decided to undertake this investigation, with Professor Buckley's permission, on ascertaining that a friend of his, an English doctor on leave from Malaya who had worked on the Siamese. Railway under the Japanese, was harbouring Strongyloides infection and had creeping eruption.

In order to carry out quantitative experiments on eelworms of the cyst forming species it is often necessary to obtain a known number of cysts from soil. The extraction of the cysts from the soil, their separation from débris which is always present, and their enumeration always take up much time. By use of the simple apparatus described below cyst separation and counting can be greatly accelerated.

The majority of normal sera proved in vitro to be cercaricidal to larvae of S. mansoni. Of 502 normal sera. 21 per cent, were noncercaricidal whereas the remainder exhibited varying degrees of cercaricidal potency.

The cercaricidal factor was thermolabile and disappeared during storage. It bore several points of similarity to complement.

The cercaricidal factor was present to a varying degree in sera from all species investigated. Apparently normal sera from all cattle and different proportions of other species, caused an enveloping precipitate to form around the cercariae. This bore no obvious relationship to the nematode worm burden or presence of F. hepatica.

An enveloping precipitate formed around cercariae of S. mansoni when placed in vitro in immune sera and incubated at 87°C. This occurred in serum immune to S. haematobium as well as to S. mansoni. It is not known-whether age and weight of infection influence the rate and extent of envelope precipitation.

A comparative study has been made of the Pseudophyllidean cestodes harboured by Pinnipeds, mainly from the Northern Hemisphere. Thirty species of this group of cestodes have been recorded in the literature, and as a result of the present study these may be divided into the following:

Valid species: Diphyllobothrium cordatum (Leuckart, 1868); D. elegans (Krabbe, 1865); D. glaciale (Cholodkovsky, 1915); D. hians (Diesing, 1850); D. lanceolatum (Krabbe, 1865); D. scoticum (Rennie & Reid, 1912); Diplogonoporus tetrapterus (v. Siebold, 1848); D. fasciatus (Krabbe, 1865); and Pyramicocephalus phocarum (Fabricius, 1780).

Investigations into the effect of internal parasitism on the digestive economy of sheep have been carried out at the Grassland Research Station, with particular reference to the effect of sub-clinical wormburdens on live-weight increase and digestive efficiency in these animals.

An experiment on six pairs of twin lambs earned out in 1946–6 was repeated in 1946–7, comparable results being obtained in the two years. One of each pair of twins was given 10,000, 15,000 or 20,000 infective larvae of Trichostrongylus axei when one month old; and four months later all the lambs were given 40 daily doses of 4,000 infective larvae of Trichostrongylus axei. Egg counts and weight gains were recorded weekly and when they were nine months old the surviving lambs were killed and examined post-mortem. The results show that the smaller doses of larvae given to lambs one month old increased their resistance to the second infestation but that the high doses (20,000 or more) decreased the resistance. There was an intermediate dosage level at which no effect, either of increased or decreased resistance, was observed.

The results of this experiment are discussed in relation to the work of other authors on resistance in animals to superinfection with parasites. It is suggested that the resistance to parasitic gastritis developed by sheep in the field may be partly a result of the intake of small numbers of larvae early in life and that it may actually be beneficial to expose young lambs to light infestations. It is, however, dangerous to expose them to a high level of infestation at an early age and because of the difficulty of assessing the dose of larvae necessary to stimulate resistance in a particular lamb, even by artificial infestation, it is impossible to make precise practical recommendations.

During the examination of the eelworms assembled after washing pieces of turf by Thorne’s sieving technique (Goodey, T., 1949), which had been collected in a meadow at Winches Farm, St. Albans, several specimens of nematodes were found, both male and female, which were first identified as Tylenchorhynchus dubius (see Thorne, 1949). On closer examination of the male tail the spicules were seen not to be the proper shape. Further examination made it clear that a different species was being looked at which had several unique features, the most characteristic being the pattern of the cuticle. This, in addition to having well-defined transverse striae, had longitudinal markings such that the whole surface was divided into minute squares and gave the appearance of very delicate and exceedingly regular quilting. It is accordingly described as a new species with the name Tylenchorhynchus tessellatus.

Pieces of Hippeastrum roots were sent to the Nematology Department, Rothamsted Experimental Station, in July, 1950, by Dr. Morris Cohen, National Agricultural Advisory Service, Northern Province. They originated from a collection of these hothouse Amaryllids at Hexham, Northumberland. Later some more pieces of root and a potted plant, which was heavily infested, were received. Dr. Cohen had found eelworms associated with lesions on the roots and in the absence of other causes, thought they might be responsible for the damage to the roots and the consequent ill-health of the bulbs during the previous few years.

The plant-parasitic nematodes have this in common with their relatives parasitic in animals, that they are unusually resistant to chemical control. It is not merely that substances lethal to the nematode are harmful to the animal or plant, for in both cases there are usually in the nematode’s life cycle free-living stages, and these are also highly resistant. Apparently the nematode cuticle, egg shell, and vitelline membrane are effective barriers to the penetration of many substances which might be expected to be good contact poisons. Several of the best modern insecticides have given disappointing results against plant eelworms (Ellis and Clayton, 1948). On the other hand some of the simpler halogenated hydrocarbons have been fairly effective, against both animal nematodes (CCl4, C2C14) and plant eelworms in the soil (C2H4Br2, C3H4Cl2).

During the course of an experiment on marine fish cultivation conducted from 1942-44 in Loch Craiglin, Argyllshire, some attention was paid to the feeding of fish as deduced from gut analyses. Most of the fish examined were flatfish and some account of their feeding has already been given (Raymont, 1947). A few round fish were also taken from time to time and a small number of these were gutted for food content.

Since the description by Looss in 1892 of the life-history of Diplodiscus subclavatus, and in 1896 of the miracidia of Gastrothylax gregarius, G. aegyptiacus and Paramphistomum cervi, there have been very few accounts of paramphistome life-histories. Gary (1909) published an account of the life-history of Diplodiscus temperatus, which Cort considered to be incorrect, and Krull and Price (1982) repeated the work on the same species. Beaver (1929) published an account of all the developmental stages of Allassostoma parvum except the sporocyst; Brumpt (1986) described the cercaria and the experimental infection of the intermediate and final hosts of P. cervi in Corsica. Willey (1941) has described the life-history and bionomics of Zygocotyle lunata, but has not given a very detailed account of the development of the egg and miracidium. The fullest account of a paramphistome has been given by Bennett (1986) of a species which was identified as Cotyhphoron cotylophorum, but which Price and Mackintosh (1944) consider to be a new species of the genus Paramphistomum, namely P. microbothrioides. Since the submission of this paper as part of a thesis for the Ph.D. degree, two further papers on the development of paramphistomes have come to the notice of the author. These are by Sinha (1950) on the development of C. cotylophorum in India, and by Willey and Godman (1951) on that of Z. lunata in America.

Although the literature contains many references to the entrance of schistosome miracidia into the snail host and their subsequent development into sporocysts and mature cercariae, there is comparatively little information available about the way these cercariae leave the snail. But the findings of Kendall and McCullough (1951) concerning the emergence of Fasciola hepatica cercariae from Limnaea truncatula, which resulted from the sectioning of infected snails, indicated that this method might also yield new information about the cercariae of S. mansoni; so at the suggestion of Professor Buckley the writer undertook the present investigation.

Although paramphistomes have been known to occur in cattle and sheep in the British Isles for-many years little precise information on the incidence, distribution and degree of infection is available. The diagnosis, except in exceptional cases, can be made only post mortem, or by the detection of eggs in the faeces. Before undertaking an investigation into this problem it was necessary to devise a simple standard technique for the collection of eggs from cattle faeces, which would be practicable not only in the laboratory but also in the field. This done, it became desirable to know firstly, within what limits egg counts were reliable criteria on which to base estimates of the number of parasites present; secondly, what was the smallest number of parasites which could be detected by faecal examination; thirdly, how much variation occurred in egg-counts from week to week in the same animals; and fourthly, if there were any variation in counts made on faeces collected at different hours of the day.