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.

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.

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.

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.