1. Excystment of the metacercariae of Fasciola hepatica by perforation of the inner cyst was witnessed, but the factors which control activation of the larva remain undetermined.

2. Excystment occurred in two instances when cysts were administered to mice by intra-peritoneal injections, active young flukes being recovered.

3. Excystment occurred when cysts were administered to one week old chicks and free flukes were recovered from the abdominal cavity in three instances, but liver lesions were not observed.

4. By means of photomicrographs an attempt has been made to demonstrate that young flukes feed primarily on hepatic cells and that they show a preference for this diet. Blood is inevitably included in the diet of young flukes, but it is claimed that these are not truly blood feeders.

5. Young flukes recovered from the liver of the mouse range in length from about 0·3 mm. at 3–4 days to 4·85 mm. at 28 days from the time cysts were administered (per os). This accords fairly well with data obtained by Sinitsin and by Schumacher in respect of flukes from rabbits and guineapigs respectively.

Several females of this new species were collected by the writer from the stomach of the Nile fish, Gymnarchus niloticus Cuvier from Khartoum in the Sudan, on June, 1958. Three males and several females were collected from the same host and locality, by Dr. Hilmy Bishai of the Zoology Department, University of Khartoum on March, 1960 and forwarded to the writer.

A half a century ago, R. T. Leiper described a new species belonging to the genus Fasciola from specimens which he collected from hippopotami at the Murchison Falls, on the Victoria Nile in Uganda, in the summer of 1907. This species, Fasciola nyanzae, was found in the bile ducts of the liver, and in most instances the specimens were somewhat macerated owing to the length of time that had elapsed before the animal could be recovered from the water. Nevertheless, the characteristic shape of these liver flukes and the restriction of the branched testes to the anterior third of the body made it possible to recognise them as being different from all other species of the genus known at that time.

Daubaylia elegans n.sp., is described from Planorbis carinatus in the Netherlands. Tables are given of the comparative measurements of the other members of the genus. The main differences between D. elegans n.sp., and these other species are the ratio length to breadth, the length of the tail, the presence of a cuticular knob on the tail of the female and the relative size of the male genital armature.

Cercaria londonensis Khan, 1900 is shown to develop into a new species of Echinosloma. The stages in the life history are described.

In an attempt to demonstrate experimentally the life cycle of Fasciola gigantica, the snails Lymnaea natalensis were exposed to newly hatched miracidia of this trematode.

Despite many recent advances in the study of nematicides and in the breeding of resistant strains of plants, control of cyst forming nematodes is still best accomplished by crop rotation; to be fully effective, it is also desirable that a field in which it is proposed to grow a susceptible crop should be sampled and an estimate made of the population of nematodes present: such an estimate is susceptible to different sources of error and although it is possible to decrease the magnitude of these errors a compromise has to be reached between the conflicting claims of precision on the one hand and the expenditure of man-power on the other; it is desirable that this compromise be based on factual data rather than guesswork; good estimates of the order of magnitude of the different types of error are therefore desirable.

Cercaria pseudocellata Szidat and Wigand, 1934; C. bilharziellae polonicae Szidat, 1929; C. kenilworthensis n.sp. and C. edgwarensis n.sp. are recorded from London. Descriptions of the two new species and a comparison with related forms is given.

Mortality in England and Wales from helminth infections as recorded in the London Bills of Mortality from 1630 to 1755 and in the Registrar-General's Annual Reports from 1837 to 1880 is analysed.

Representatives of the ‘Lophocercous’ group are recorded from Britain for the first time. Two new species are described and a summary of the classification of this group is discussed.

1. The behaviour and development of Brugia patei has been followed in the mosquito host, Mansonia uniformis, from ingestion of the microfilariae to the development of the infective stages.

2. The microfilariae penetrated very rapidly out of the stomach into the abdomen of the mosquito; 80% of them escape from the stomach during the first 50 minutes after a blood meal.

3. The microfilariae migrate from the abdomen to the thorax through fat body cells and the heart during the first 140 minutes followed engorgement and begin to penetrate the indirect flight muscles within 15 minutes from engorgement. During this migration microfilariae were found in close association, suggesting that they follow similar pathways of migration through the body of the mosquito.

4. Most microfilariae (98%) have settled in the indirect flight muscles within 2 hours of engorgement. In these muscles the larvae digest away the muscle surrounding them but do not begin to elongate until the third or fourth day after the blood meal. The rate of development varies from one mosquito host to another, but about 80% of the larvae have developed to the infective stage by the ninth to tenth days after the infective feed. The infective stages concentrate in the head and proboscis of the mosquito vector. The development of B. patei is faster than that of B. pahangi in mosquitoes from the same colony.

5. The efficiency of M. uniformis as a vector of B. patei is compared with the similar efficiency of M. longipalpis as a vector of B. malayi. In both mosquitoes the majority of the microfilariae ingested develop to the infective stage. M. uniforms is also an efficient vector of B. pahangi.

6. The development of the parasite is discussed briefly with reference to knowledge of the physiological events within the mosquito host subsequent to the blood meal.

Roots of oats grown on sandy loam in Norfolk were observed by E. B. Brown of the National Agricultural Advisory Service, Cambridge, to have small galls associated with proliferation of the lateral roots. Close examination showed the presence of female Meloidogyne in the galls. The nematodes differed in some respects from the generally-known species and specimens were sent to the author for study.

1. The morphology of the adult worms and the microfilariae are described of a new species of filarial worm, Dipetalonema manson-bahri.

2. Dehpsylla crassipes Jordon, 192G, a flea specific to Pedetes surdasler, was found in nature to contain infective larvae which are believed to be those of D. manson-bahri.

3. In the laboratory full development of D. manson-bahri was observed in Ctenocephalides felis and Xenopsylla cheopis.

Observations were made on the biology of Cotylophoron cotylophum in respect of the hatching of miracidia, infection of the intermediary mollusc, emergence and encystment of cercariae, and on the pathogenicity of the parasite. It was noted that miracidia of this parasite hatch in 15 days at a temperature of 28-30°C. At a lower or higher temperature than this hatching is delayed. When the miracidia are mature a sudden fall in temperature hastens their hatching. Darkness has no adverse effect on hatching. These miracidia show a marked attraction towards Indoplanorbis exustus, which are proven to be the intermediary molluscs of this amphistome. At room temperature, ranging between 21-24°C. during the day and 18-21°C. at night, sporocysts develop within the snails in about 24 hours and on the 4th day rediae are seen developing inside the sporocysts.

Les conceptions concernant les propriétées de la cortisone et l'ACTH ont beaucoup évolué. On considérait ces hormones commenuisibles dans les infections bactériennes et parasitaires puisque leur principale propriété est de neutraliser la réaction inflammatoire, histiocytaire et macrophagique. Or dans beaucoup de cas on a observé des résultats favorables dans différentes infections, et on a fait remarquer que plus le processus septicémique est sévère, meilleur est l'effet obtenu. Dans les infections à protozoaires sanguicoles les résultats sont extrèmement divergents même chez l'homme.

1. A new genus and species of Isoparorchiidae Poche, 1926, is described from the air-bladder of the marine catfish, Anus jella (Val.), caught off the coast of Waltair, India. The new fluke is named Elongoparorchis pneumatis.

2. The new genus Elongoparorchis bears a superficial resemblance to the genus Isoparorchis Southwell, 1913, but differs appreciably in the structure of the testes, the ovary and the vitellaria to warrant the separation.

During systematic studies of helminths of reptiles and birds the writer found a very interesting cestode which was collected from Agama cyanogastcr and is described here as Megacapsula leipcr.i gen. et sp. nov. Two other cestodes, Oochoristica zonuri Baylis, 1919, and Arostellina rcticulala Neiland, 1955, are recorded from new hosts and are redescribed.

Pulmoverminae is proposed as a new subfamily within the Hemiuridae Lühe, 1901, to receive the genera Pulmovermis Coil and Kuntz, 1960 and Hydrophitrema Sandars, 1960. The genera are compared, and considered to be distinct.

Confusion exists about the true nature of the guiding apparatus surrounding the spear in Dorylaims. Thorne and Swanger (1936), commenting on the guiding ring, say: “There are at least two types; the collapsible cylindrical form with cutinized borders that give the appearance of a “double” ring such as that of Dorylaimus stagnalis (Fig. 2A), and the single muscular ring as found in D. obscurus (Fig. 2E). From the guiding ring a thin sheath envelops the spear to its base”.

A redescription is given of the morphology of the bladder (normal) and branchial (neotenic) forms and the structure'of the larva of Polystoma integerrimum, including a description of the histological changes accompanying digestion, and an account of the peripheral sensory system of the bladder adult.