A biological study of the fauna of sewage-treatment plants was pursued by the writer for two years, from June 1927, thanks to the generosity of the Grocers' Company. The programme laid down included a qualitative and quantitative survey of the fauna and a collection of data on such physico-chemical factors as hydrogen ion concentration and oxygen requirement, with a view to seeking correlations between the two groups of phenomena.

Fourteen species of parasitic worms recovered from Adenota kob thomasi (P. L. Sclater) in Uganda, Africa, are recorded.

The morphology of two tapeworms, Moniezia monardi Fuhrmann, 1931 and Avitellina buechneri sp. nov., is described in detail and discussed.

Twelve sheathbills, Chionis alba, 12 South Georgian diving petrels, Pelecanoides georgicus, and 5 common diving petrels, P. urinatrix, collected at Bird Island, South Georgia, were examined for helminth parasites. These appear to be the first helminthological examinations of birds from South Georgia. Eleven of the 12 sheathbills were infected with helminth parasites and the pattern of infection of adult male and female birds was similar. Five species of helminths were found in sheathbills, namely Gymnophallus dellciosus, Notocotylus chionis, Paramonostomum signiensis, Lateriporus australis and Corynosoma hammani. Two species, namely Tetrabothrius sp. and Stegophorus heardi, were found in both Pelecanoides georgicus and P. urinatrix.

The helminth parasites of whales and seals in the Antarctic and Subantarctic have been extensively studied, while in comparison those of birds from these regions have been neglected. As far as we are aware there are no previous reports on helminth parasites from the sheathbill, Chionis alba (Gmelin), the South Georgian diving petrel, Pelecanoides georgicus (Murphy and Harper), and the common diving petrel, P. urinatrix (Gmelin), from South Georgia.

Irradiation-attenuated helminth parasites have been used in protection against homologous challenge (reviewed by Cox, 1978). The exact dose of irradiation required to attenuate without loss of immunogenicity varies between different species; determination of the dosage and difinition of the effects of irradiation is therefore a vital preliminary step.

Conventional methods for percutaneous infection of rats using third-stage juveniles of Nippostrongylus brasiliensis which have been artificially stimulated to exsheath lead to highly variable, and relatively poor, establishment in the intestine. A new system has been developed in which larvae applied to the skin still remain partially sheathed, as they would be in nature. Cultures of the freeliving stages of the parasite contain an annulus of clear, colourless polythene film to which some of the third-stage juveniles attach. Rats are infected with an individually counted, exact dose applied to the skin on polythene. Using this technique (‘EDT20Nb’), consistently high values for the mean proportion of the dose that becomes established have been obtained, along with a variance well below the normally accepted level ( from a total of 73 rats in 12 separate assays). In particular, the added component of variance between assays in this study was insignificant, so that the probability of quantitative agreement in replicate experiments based on the method is high. It is recommended for an experimental design in which small numbers of parasites can be used.

A functional buccal stylet is described in adult male and female Trichinella spiralis, and the mode of feeding of the adults is described from living specimens examined immediately on removal from the intestine. The stylet is rapidly protruded and retracted, probably for lacerating host tissue and releasing tissue fluids, and active peristaltic sucking movements of the pseudo-bulb of the oesophagus take place about once a second. The rectum shows peristaltic defaecatory movements once every two or three seconds. Intra-vitam staining with 0·01% neutral red shows an acid reaction of the stichocytes of the stichosome, which are of a granular or non-granular nature, with small tubules and alveoli in the cytoplasm.

The structure of the digestive tract of Euclinostomum multicaecum (Digenea: Euclinostomatidae) is unusual, comprising several main lateral caeca which extend posteriorly and further divide, giving rise to numerous smaller branches which are widely distributed throughout the fluke. These multicaeca presumably promote nutrient absorption during rapid and prolonged feeding directly following excystment. The caecal wall consists of a syncytial gastrodermal epithelium, bearing loop-like lamellae which extend into the lumen and enclose spherical inclusion bodies and presumably also, increase the absorptive surface area. There was no evidence of endo- or exocytosis, nor were lysosomes, phagosomes or residual bodies observed. The gut caeca are supported by a fibrous basal lamina and an underlying layer of muscle fibres, while parenchymal cells occupy much of the extracellular space. The protonephridial system resembles that observed in other digeneans consisting of flame cells and collecting ducts which join to form a bladder that opens externally through a single excretory pore. The syncytial epithelium of the collecting ducts is elevated by numerous lamellae while the basal lamina is highly infolded. The luminal contents of these ducts comprise bar-shaped crystalline structures, lipid droplets and electron-dense inclusion bodies. The excretory system is supported by a network of muscle fibres and parenchymal cells.

Two new species of Avitellina, A. woodlandi and A. tatia, have been described and separated from the allied species of the genus. Both these species are remarkable for having cirrus sac longer than vulva.

Additional data are provided in regard to the structure of the species A. sudanea, A. lahorea and A. chalmersi.

The development of the female genitalia of A. chalmersi, which may be regarded as typical of the genus, has been given in detail for the first time.

New observations on the development of the inner column of testes in A. sudanea are made.

A review of the existing species of Avitellina has been taken and a key to all the known species of the genus has been given.

Parasitological and clinico-pathological aspects of Schistosoma intercalatum infection in sheep were studied after exposure to 5000 cercariae per animal. It was shown that the infection, in spite of relatively high tissue egg counts, only gave rise to low-grade clinico-pathological manifestations with almost unaffected blood parameters. The parasites were mainly located in the lower part of the intestinal tract, and the number of eggs being passed in faeces was very low.

Description: The specimens were collected from three Bartailed Godwits shot in the winters of 1956 and 1957. The description below applies mainly to the first infestation found. There are certain differences between the infestations which are noted later. There were up to 150 individuals in each infestation, varying from immature worms consisting of a scolex and a few proglottides to mature strobilas containing some 300 segments and reaching a length of 75 mm. The maximum breadth of the strobila is 1·8 mm. The onset of maturity is accompanied by a marked increase in the breadth of the strobila and the mature proglottides are broader than long.

Until 1934 the life history of Syngamus trachea was usually considered to be direct though Walker in 1886 and Waite in 1920 had both tentatively suggested that earthworms play a part in the dissemination of the parasite. In that year, however, I was able to show conclusively in this laboratory that the rôle they play in transmitting the nematode is a very important one, for by means of this annelid it was possible to effect with certainty heavy infections in various birds of domestic importance. The following year it was shown also that Syngamus from starlings can easily be transmitted to chickens by earthworms: this method apparently overcomes the resistance due to a different “host strain” such as Taylor had previously encountered when he tried to infect chickens directly with material obtained from starlings. In 1938 using earthworms as vectors chickens, pheasants and partridges were easily given definite infections with various other “strains” of Syngamus. Consideration of these results made it no longer possible to ignore the importance of earthworms in the life cycle of “Gapes.”

The rate of glucose absorption and metabolism and the associated fluid transfer of the small intestine of rats was measured in vitro using an everted sac technique after daily doses of 0, 5, 25 or 225 infective larvae of Nippostrongylus for periods of one to five weeks. Though there were occasional significant changes in the physiology of the intestine there were no obvious patterns or trends with respect to time at any infection level. This differs from the response after a single infection. The possible role of immune adaptation and reduced immunogenicity of the worms during repeated infections is considered.

That the infective larvæ of a number of species of hookworm are capable of penetrating intact skin has been demonstrated in the following, Ancylostoma duodenale, A. caninum, A. braziliense and Necator americanus.

Lung infection with Angiostrongylus cantonensis was established in experimentally infected Indian softfurred rats (Millardia meltada) and Indian spiny mice (Mus platythrix). Pulmonary arterial migration occurred earlier (at day 20 after infection) in M. meltada than in Wistar rats. M. meltada and M. platythrix could serve as useful animal models for comparative studies of mechanisms determining host specificity of A. cantonensis.

The aims of this study were to determine the frequency of egg shedding (percentage of egg-positive faecal samples) and faecal egg counts (FEC) over 13 months in two different breeds of ewes, both pregnant and non-pregnant, in a mountainous region of central Mexico. Additionally, the effect of ivermectin and albendazole treatments on FEC reduction was recorded. The study also aimed to relate temperature and rainfall to FEC. The gastrointestinal nematode (GIN) third-stage larvae genera recovered from both faeces and grassland pastures in a temperate region were also assessed. Faecal samples were collected from ewes at monthly intervals for 13 months to investigate the FEC population of GIN larvae, their concentration and genera in grass samples collected from grazed and rested pastures. Egg-shedding frequency ranged from 0 to 92% and FEC from 0 to 12,000 eggs per g faeces (epg), with counts in Suffolk higher than in Dorset ewes. The identified genera were Haemonchus, Trichostrongylus, Teladorsagia, Cooperia, Oesophagostomum, Bunostomum, Nematodirus and Strongyloides. Haemonchus and Trichostrongylus were the most common genera. The number of L3 was higher in grazing lands than in those at rest. The highest FEC were recorded in the dry season due to peripartum, but the highest L3 counts were recorded in the rainy season. The coexistence of species of different geographical distributions at this site may be because there is a confluence of Nearctic and Neotropical geographic regions; thus, despite the temperate climate, tropical species can be found. Additionally, this study suggests that increasing temperatures could favour the presence of different tropical GIN species together with typical temperate-zone GIN species.

Drasche in Stossich established the genus Oxyspirura in 1897 for Cheilospirura cephaloptera Diesing 1861, previously described by Molin in 1800, along with two more species, all as belonging to Spiroptera. Since the establishment of this genus, as many as thirtysix species have been reported from various parts of the world. The distribution of this worm is very wide and the number of species seems to be much more than what has already been described. The writer collected nine species from the orbital cavities of birds, and all turned out to be new ones.

In 1931, Skrjabin divided the genus Oxyspirura into three subgenera, i.e. Oxyspirura, Cramispirura and Yorkeispirura, on the basis of the divided buccal capsule (Yorkeispirura) and undivided buccal capsules (Oxyspirura and Cramispirura); and also on the equal spicules (Cramispirura) and unequal spicules (Oxyspirura). The writer based the present key to the species of the genus on the same criteria. Species belonging to Yorkeispirura and Cramispirura are not included in this key.

This paper concerns the relationships between miracidia of Schistosoma haematobium from Aden and various species of the Bulinus complex. It includes evidence on penetration and further development within the snail as revealed in serial sections.

The kinetics of Breinlia booliati infection in 3 inbred rat strains (Lewis, Wistar and Sprague Dawley) were investigated. One group of rats was infected as neonates (less than 24 hours of age) with third-stage larvae of B. booliati and the other group was infected as juveniles (4 weeks of age). The results showed that infection in the neonates were significantly different from the infection in the juveniles. The 60 rats infected as neonates, when necropsied between 8 to 10 months postinfection, yielded adult worms. The 2 neonatal infection groups of Lewis and Wistar strains showed highest susceptibility to the infections. The mean prepatent period was 85 days. Ninety to 95% of the infected rats were patent with microfilaraemia and a large percentage (33 to 47%) of them had high microfilaraemia counts exceeding 3000 mff/20 mm3 of blood and larger sizes (mean 157·11 mm for female adult worms and 61·88 mm for male adult worms. The adult worms were distributed equally in both the pleural (57%) and peritoneal cavity (43%). In most aspects, the neonatal infection group of the Sprague-Dawley strain was intermediate in susceptibility between the 2 neonatal infection groups of the Lewis and Wistar strains and the 3 juvenile infection groups. In contrast to neonatal infection groups, the 3 juvenile infection groups exhibited low infection rates (37%, 58% and 47% for the Lewis, Wistar and Sprague Dawley strains respectively), longer prepatent periods (mean 101 days), lower recovery rates (2 to 4%), lower adult worm loads (mean 0·4 to 0·8 female worms, and 0·2 to 0·8 male worms per rat), and smaller sizes (mean 141·24 mm for female adult worms and 53·75 mm for male adult worms). Forty-four to 57% of these infected rats harboured either single male or single female adult worms in the body cavity. Most (92%) of the adult worms recovered from the juvenile infection groups resided in the pleural cavity and the remaining 8% were recovered from the peritoneal cavity. Microfilaraemia could be detected in only 3/20 Lewis rats, 5/20 Wistar rats and 5/20 Sprague Dawley rats. The mean peak microfilaraemia of the 3 pooled juvenile infection groups was 632 mff/20 mm3 of blood, ranging from 7 mff/20 mm3 to 1856 mmf/20 mm3. Our results indicate that the susceptibility to B. booliati infection in white rats is both genetic and age-associated. The responses of the 2 distinct infection groups to B. booliati infections are discussed.

5′-nucleotidases of eight species of digenetic trematodes were studied using five different substrates. All species showed the following preferential order of substrate affinity; AMP>CMP>GMP>TMP>UMP. It was observed that different species occupying similar habitats possessed closely related levels of enzyme activities. The function of 5′-nucleotidases in trematodes is also suggested.

Parasite composition can be affected by physiological and ecological changes during host ontogeny. Intertidal fish do not travel long distances and live in the same area throughout their lifetimes, meaning that parasite communities can differ across geographic ranges. The objective of this study was to analyse the parasite communities of three fish species (Hypsoblennius sordidus, Helcogrammoides cunninghami and Scartichthys viridis) collected from the Chilean coast. The composition of parasite species was compared among host ontogenetic stages (larvae, juveniles and mature fish) and geographic areas. A total of 184 larval, 252 juveniles and 217 mature individuals were collected in the northern area (c. 24°S), and 186 larval, 192 juveniles and 112 mature individuals from the central area (c. 33°S). Ectoparasites were most prevalent in fish from the central area, whereas endoparasites were most prevalent in the northern area. The parasite species richness varied significantly between geographical areas for H. sordidus and H. cunninghami, but the parasite composition varied significantly between geographical areas for all fish species analysed. Therefore, the geographical area was the most important factor determining the parasite composition of intertidal fish species. The absence of endoparasites in fish larvae and the increased infestation in juvenile and mature fish may be explained by the shift in habitat from the water column to intertidal pools where prey abundance and availability are higher. On the other hand, hydrographic barriers affecting prey distributions may also offer an explanation as to the differences in parasite composition.