The immature stages of Caraphractus cinctus Walker are described.

Four larval stages have been observed which may correspond to three or four instars. In no stage have mandibles been observed.

The first-instar larva is elongated and active. In the second-instar oral lobes are present. In the next stage the larva becomes shapeless and rather transparent. In the last stage the wall of the mid-gut shows conspicuous opaque spots which consist of single cells containing spherical concretions, probably the products of excretion.

These concretions later become free in the gut of the pupa and are discharged in the meconium when the imago emerges from the host egg.

The effects of parasitism on the host eggs of different ages is discussed. In newly laid host eggs all the contents are consumed by the parasitic larvae. In advanced eggs of Agabus the egg of Caraphractus is laid in the mid-gut of the host embryo where the parasitic larva develops, the hard parts of the host larva remaining intact. Parasitism in advanced eggs of Dytiscus is rarely successful.

The larvae of other Mymaridae are discussed and their main features compared. The first-instar larva of Caraphractus does not correspond to any of the previously described types of mymarid larvae.

The seasonal history is described, with the sequence of hosts parasitized throughout the year. From four to six generations of Caraphractus have been bred indoors during the year. The winter is passed as a diapausing prepupa. In some cases diapause may be prolonged. Fertility is high: 121 imagines have been bred from one female of Caraphractus.

I have much pleasure in acknowledging my gratitude to the late Dr W. D. Hincks for his kindness in reading the typescript of this paper: the comments by such a well-known authority on Mymaridae have been most valuable. I am very grateful to Mr O. Bakkendorf for allowing me to reproduce several of his figures of Mymarid larvae from the valuable work he devoted to the biology of Danish hymenopterous egg-parasites. I am also grateful to Miss B. A. Trott of the Commonwealth Institute of Entomology for the help she has so kindly given me with references.

The following list, compiled during my tenure of a grant given by the Nuffield Foundation to the Wildfowl Trust, Slimbridge, Gloucestershire, records species of Protozoa, helminths and Arthropoda found in anatid birds, either by the authors of the papers listed in the References, or by others to whose work these authors refer. It will be seen that there are, after the names of all the parasites, numbers which indicate, by reference to the corresponding numbers in the References, the authors and publications in which the species concerned are recorded. Thus Cotylurus brevis (142, 145*) means that this trematode was recorded from Aix galericulata, the Mandarin Duck, by Dubois (1953) and that Dubois & Rausch (1950a) reported an experimental infection of this duck with it.

Outdoor observations were made on the rate of development of the free-living stages of O. ostertagi at different times of the year, and on the migratory activities and longevity of the larvae in faeces, on herbage and in soil.

The effect of temperature on the rate of development of eggs and larvae in faeces, and the effect of temperature and humidity on the longevity of eggs and larvae when separated from faeces, were studied in the laboratory.

The results of these observations are discussed in relation to translation (that is, the process whereby eggs in faeces become infective larvae on herbage available to the grazing animal) and to the transmission of infection in the field.

I wish to thank Mr J. F. Michel for providing the infected faeces, and Mr D. A. Griffiths for technical assistance.

The post-cercarial development of G. crumenifer (Creplin) has been experimentally elucidated.

Gyraulus convexiusculus (Hutton) serves as the intermediate host under natural conditions.

The adult stage of the fluke was raised experimentally in ruminants, the time taken by the parasite to attain maturity being 118 days in the kid and 114 in the buffalo calf.

Cercaria chungathi Peter & Srivastava, 1955, has been established to be the larva of Gastrothylax crumenifer. The cercaria, the redial parthenita and the metacercaria have been described.

The authors are grateful to the Director, Indian Veterinary Research Institute, for his keen interest in these studies.

A description is given of two new Cephaline gregarines from Indian crickets collected at Lucknow and Jalaun, United Provinces.

One of these, Stenophora gryllodes-sigillatae sp.nov., from the gut of Gryllodes sigillatus, has solitary slender trophozoites up to 194μ long. Its epimerite is rounded in young forms and absent or represented by its remnant in adults. The nucleus has two chromosomes. Cysts are rounded, invested in a very thin membrane and without sporoducts.

The second, Bulbocephalus indicus sp.nov., from the gut of Liogryllus bimaculatus, is characterized by solitary elongated sporadins; the neck is short and a bulbous epimerite is always present. The body, measuring up to 175μ in length and up to 30μ in breadth, presents a striated appearance. Cysts are oval, covered by a very thin membrane, and have no sporoducts.

The author is very grateful to Dr S. M. Das, under whose able guidance this work was carried out. His thanks are also due to the Department of Zoology, University of Lucknow, for providing the laboratory facilities.

1. A qualitative and semi-quantitative analysis of the free amino acids in the haemolymph of Rhodnius prolixus has been made by paper chromatography.

2. Twenty-one amino acids or related compounds were detected of which histidine appears at the highest concentration.

3. The α-amino-N concentration of haemolymph is among the lowest values recorded for insect haemolymphs.

4. A substance corresponding in position to thyroxine has been detected in haemolymph of a few immature insects, and is formed if iodate is added to freshly withdrawn haemolymph.

I wish to record my great appreciation to the late Professor P. A. Buxton, C.M.G., F.R.S., for his valuable assistance and criticism during this study and to members of the staff for helpful discussions. The study forms part of a Thesis for the degree of Ph.D. approved by the University of London, and was financed by the South African Council for Scientific and Industrial Research whose generous support I acknowledge with pleasure.

1. A qualitative paper chromatographic analysis of the free amino acids in Rhodnius urine and excreta was made: eleven amino acids or related compounds were detected, cystine and cysteic acid in urine, and histidine, histamine, leucine, taurine, glycine, valine, phenylalanine and alanine in the excretory fractions.

2. In addition to these, three yellow pigment spots were separated from the excreta; one of these is of unknown composition and two are peptides.

3. A possible relationship between certain of the excretory amino acids and haemolymph ones is discussed.

I am greatly indebted to the late Professor P. A. Buxton, C.M.G., F.R.S., for his stimulating criticism during this study, and to the members of the School for very useful discussion, and to Mr Paul Baily for performing the column chromatographic analyses on my behalf. The study forms part of a Thesis for the degree of Ph.D. approved by the University of London, and was financed by the South African Council for Scientific and Industrial Research. I wish to acknowledge their generous financial support.

In November 1953, about one-half per cent of Lymnaea luteola taken from a pond in Alfred Park, Allahabad, were infected with an echinostome cercaria. The first collections of these cercariae were made by Dr Onkar Nath Srivastava, who was surveying cercarial infections in the snails and who kindly gave me the echinostome material. Additional material was obtained by numerous subsequent collections. After the cercaria was described it was possible to undertake a limited number of experiments in an attempt to discover other stages of the life cycle. It was found that Lymnaea luteola is both the first and the second intermediate host of a new species of Echninoparyphium. The adult of this new species, for which the name E. bagulai is proposed, matures in the intestine of the domestic duck, Anas poecilorhyncha. When this duck was experimentally infected with cercariae, the adult trematode was recovered from the intestine of this duck 21 days after its infection.

Third and artificially hatched second-stage larvae of A. suum were exposed to the action of saline and normal and homologous immune pig serum. Precipitates developed at the mouth, excretory pore, anus and around the cuticle of third-stage larvae when they were placed in immune pig serum, but not in saline or normal serum. Precipitate was most evident at the excretory pore and was often the first precipitate to form. It is suggested that the excretory products may play an important role in stimulating the production of antibody in the host. A relationship was noted between the antibody titre of the serum and the amount of precipitate, the life span of the larvae, their activity, and the rate at which precipitates formed. It is concluded that the titre of the serum was in some degree a measure of the ability of the host to resist reinfection.

Circumlarval precipitates did not form when second-stage larvae were placed in samples of the same immune serum. It is pointed out that this may be due to the lack of sufficient antigenic material available to react with antibody in the antisera. It is also suggested that an absence of sufficient larval antigen may also partly account for the small degree of resistance exhibited by the resistant host within the first 2 or 3 days of reinfection.

The work, which is abstracted from a Ph.D. thesis, was carried out in 1957 under the tenure of an Animal Health Trust Wellcome Fellowship. I am grateful to Dr Soulsby, under whose guidance this work was carried out.

The excretory systems of Gastrothylax crumenifer, Fischoederius elongatus and F. cobboldi have been described. In all three species it shows the characteristic, more or less H-shaped, pattern of the amphistome excretory system.

The difference between the systems in the three species lies in the nature of the branches of the anterior portions of the longitudinal excretory ducts, in the transverse excretory ducts and the branches received by them and in the number of flame cells at the ends of the capillaries.

The main longitudinal excretory ducts run internal to the intestinal caeca in G. crumenifer and F. cobboldi, while in F. elongatus they run almost external to the caeca and maintain this position even in the posterior half of the body, where the caeca are not present.

1. Neodiplostomum intermedium Pearson is recorded from four new hosts; as an adult from the water rat, Hydromys chrysogaster Geoffroy, and as a metacercaria (diplostomulum), from tadpole and adult of an undescribed tree frog, Hyla sp., tadpole of (Hyla latopalmata (Günther) Mixophyes fasciolatus Günther and frog of an unidentified leptodactylid.

2. The life cycle of Neodiplostomum intermedium was followed experimentally; the hosts were: Pettancylus assimilis (Petterd), a fresh-water limpet, as first intermediate host; tadpole of Hyla pearsoni Copland as second intermediate host; Hyla caerulea (Shaw) a tree frog, and Hemisphaerodon gerrardi Peters, the pinktongued skink, as paratenic hosts; and Rattus assimilis (Gould) and laboratory rats as definitive hosts.

3. Descriptions are given of the morphology of the miracidium, mother sporocyst, daughter sporocyst, cercaria, and diplostomulum, with special reference to the structure of the miracidium and of the cercarial tail.

4. Observations are given on the embryology of the miracidium, hatching of the egg, transformation of the miracidium into the mother sporocyst with special reference to the germinal cells, the route and manner of escape of cercariae from the snail host, the development of the diplostomulum with special reference to the reserve excretory system, and the movements of diplostomula during metamorphosis of the tadpole host.

5. The haploid chromosome number is ten, as determined from squashes of testes. One paratype and a series of experimental adults have been compared with and found different from Neodiplostomum (Fibricola) sarcophilus n.comb. The orthography and formal proposing of the names of the species of Fibricola transferred to Neodiplostomum by Pearson (1959b) are corrected.

The writer wishes to thank Dr M. J. Mackerras, Queensland Institute for Medical Research, for generously supplying water rats; Professor J. F. A. Sprent, University of Queensland Veterinary School, for his criticism of the manuscript; Mr K. Webber and his sons for their assistance in catching rats and for permission to collect snails, frogs and tadpoles from their streams; and Mr R. J. Ballantyne for technical assistance. This study was supported by a grant from the Rural Credits Fund of the Commonwealth Bank of Australia.

1. Studies have been made of carbohydrate metabolism in Fasciola gigantica during starvation and these are compared with data available about carbohydrate metabolism in F. hepatica.

2. In F. gigantica the glycogen content before starvation was 5·4% of f.w. or 25·35% of D.W. of tissue, and the glycogen content after starvation was 3·5% of F.W. or 16·29% of D.W. of tissue.

3. The medium in which F. gigantica was incubated was analysed for lactic acid as one of the end products of glycogen consumption. The lactic acid given out in a period of 2 hr. was 0·46% of F.W. or 2·18% of D.W. of tissue.

I wish to thank Professor K. Sahai for his generous help in the preparation of this manuscript.

An in vivo test is described for the screening of compounds for anthelmintic activity using Hymenolepsis nana var fraterna in mice. Results obtained with known taenicides and taenifuges are tabled, analysed and compared with their action against the tapeworms of larger animals including man.

My thanks are due to Messrs Boots Pure Drug Co. for permission to publish, Mr J. W. G. Leiper, F.R.C.V.S. for his help and advice, and Miss J. Smith for her able technical assistance.

1. It has been shown that there is a difference between the resistance of male and female mice to infection with Nematospiroides dubius.

2. More parasites were harboured, during both the larval and adult parasitic phases, by male mice.

3. These worms were found to occupy a similar relative length of the intestine between the stomach and the caecum in male and female mice infected for either 5 or 10 days.

4. The relative length of the intestine infected on the fifth day was significantly greater than that infected on the tenth day.

This investigation was carried out during the tenure of a Research Studentship from the Department of Scientific and Industrial Research. I should like to thank Professor I. Chester Jones, in whose department the work was done, for the facilities provided and Dr E. T. B. Francis for his helpful and critical supervision.

The LD50 of Nippostrongylus muris for outbred hooded rats has been estimated. It was higher for males than for females and this does not appear to be due to weight differences. The distribution of times of death was bimodal; the peaks corresponding to different stages in the life cycle of the worm.

We wish to thank Mrs M. Whitehead for technical assistance and Mr I. McDonald for statistical analysis.

1. Histological data are given about the location and frequency of the different stages of the life history of D. folliculorum in the pilo-sebaceous apparatus of man. These data are examined statistically and the relative durations of each stage and their movements in the follicle are deduced from them.

2. A method of in vitro culture is described and data are given about the longevity of the various stages of the life history.

3. Experiments on the behaviour of the different motile stages of the mite are described. It is concluded that the deutonymph is the distributive stage, and that distribution occurs over the skin surface.

4. The life history is reconstructed by a synthesis of the evidence presented. The life-cycle lasts approximately 14½ days, the life span of each stage of it being: ovum 60 hr., larva 36 hr., protonymph 72 hr., deutonymph 60 hr., adult 120 hr. Interval between copulation and oviposition 12 hr.

This work was largely carried out in the Department of Pathology of the Institute of Dermatology, London, and I wish to thank the Director of Pathology, Dr J. O. Oliver, for making available to me the facilities of his department, and for his advice and interest during the progress of the work. The photographs were prepared by Mr R. H. Lunnan of the Photographic Department of the Institute of Dermatology. I am indebted to the Dean of the Institute of Dermatology for permission to publish the photographs.

I am grateful to Mr T. E. Hughes of the Department of Zoology, Birkbeck College, University of London, for his advice at all times, and to Miss Hilda Davies of the Department of Statistics, University of Sheffield, for help with statistical methods and to Mr W. Moseley, who prepared the text figures.

Finally, I wish to express my thanks to Professor I. Chester Jones and Dr E. T. B. Francis of the Department of Zoology, University of Sheffield, for reading the manuscript and for their help in its preparation.

Rats were given immunizing doses of N. muris larvae by three different routes: orally and intraperitoneally and through the skin. The immunized rats survived a test infection which was lethal for non-immune rats. Only the rats immunized by the skin route showed skin sensitivity.

1. Echinobothrium brachysoma Pintner and E. affine Diesing have been found in the spiral valve of Raja clavata L. off the coast of Britain.

2. The spiral valve is lined by tubular crypts into which the scolices of the worms are thrust, the strobila, with one gravid proglottid, being free in the lumen.

3. The functional morphology of the scolex of E. brachysoma has been described. That of E. affine appears to be similar.

4. The scolex adheres, mainly, by the apical hooks which can be raised by inner and outer elevator muscles attached to their roots and closely associated with the rostellum.

5. The rostellum can be protruded by the contraction of a dorsal and a ventral protractor muscle. Movements of the rostellum elongate the scolex in a dorsoventral direction, forcing the apical hooks against the crypt wall and supporting them.

6. The peduncle hooks are not often embedded in the epithelium. Both series of hooks damage the epithelial lining of the crypt.

7. The remaining musculature, excretory and nervous systems are described.

8. The genitalia are essentially the same in both species. The number of testes varies from one proglottid to another in the same worm. In E. brachysoma the mid-ventral genital atrium is near the posterior end which affects the course of the vagina. The eggs in both species include two yolk cells which are similar to those of the Digenea and Pseudophyllidea.

The species of Astomatous ciliates of the genus Metaradiophrya dealt with in the present paper inhabit the intestine of three species of earthworms. They are, together with their hosts, as follows:

Two attempts to transfer immunity against N. muris to rats using the lymph node and spleen cells from actively immunized donors were unsuccessful. Experiments showed that the rats were sufficiently inbred, that the transfer technique was satisfactory, and that the donors were adequately immunized. The rats' competence as donors for adoptive transfer was demonstrated with sheep red cells as antigen. The adoptive transfer of immunity against sheep red cells was successful in recipients whose donors had sheep red cells only and no N. muris. There was no detectable transfer of immunity against N. muris or sheep red cells to recipients whose donors had received both.

We are very grateful to Miss Kathleen O'Brien for technical assistance, to Professor P. B. Medawar, F.R.S., for his help and advice and to Dr E. J. Delorme for showing us Professor M. F. A. Woodruff's skin-grafting technique.