From 24 May to 4 July 1961 about 12,000 roach, Rutilus rutilus (L.), died in a lake at Brynmill Park, Swansea, South Wales. Even this high figure may be an underestimate of the actual mortality rate as it is based entirely on extractions of dead fish from the surface waters by members of the Brynmill and District Angling Club, who used landing nets from the shore only, although at fairly regular intervals. The daily counts of dead roach are represented on a histogram (Text-fig. 1). It is also of interest that in the early summer of 1961 large numbers of roach succumbed in other regions of the British Isles; about 30,000 died in the River Trent, Derbyshire, and 3000 in the lake in St James's Park, London. Newspaper reports in both localities attributed the cause to a deficiency of oxygen. For the outbreak in South Wales, however, similar reports suggested that ‘white spot disease’ caused by the ciliated protozoan Ichthyophthirius was responsible for the mortality.

The successful rearing of Amblyomma sparsum, using rabbits as larval and nymphal hosts and either sheep or tortoise for feeding adults, is described and details of the duration of the various stages are given. The life cycle of this tick is compared with that of A. variegatum and A. nuttalli.

The authors are grateful to the Director of the Coryndon Memorial Museum, Nairobi, for the loan of a Leopard Tortoise, and to the Directors of the East African Veterinary Research Organization and of the Veterinary Services, Kenya, for permission to publish this note.

Samples of the snail Velacumantus australis from an area of 10 yards in diameter, were examined to determine if the incidence of larval trematodes varied with the density of the snails. The incidence in susceptible snails from areas where the density was less than 20 snails/sq. ft. was found to be significantly greater than in snails from areas where the density was higher than this. Further analysis showed that the variation in incidence, with density, was due almost entirely to the juvenile part of the population.

Success in immunizing rabbits, rats and sheep with dead trypanosomes depends on the method of killing trypanosomes, the frequency of inoculations, and the strain used for immunization. Positive results were obtained when trypanosomes were killed by formalin or by freezing and thawing five times. Negative results were obtained when trypanosomes were killed by 56° C. for half an hour.

Animals which received 10 doses of the mixture produced better results than those which received the same amount but only in 2 doses. An addition of Freund's adjuvant improved results, but 10 doses without an adjuvant were still better than 2 doses with an adjuvant. When trypanosomes were killed by 0·5% formalin, only an M variant of T. brucei, which was maintained by frequent passage in mice and was an antibody-sensitive variant, was able to produce in animals protective antibodies and resistance to a homologous ‘M’ variant, but not to an ‘R’ variant. On the other hand, if an ‘R’ variant of the same strain, which was passaged forty-eight times through rabbits and became resistant to antibodies, was killed by 0·5 % formalin and inoculated into animals, no antibodies and resistance could be demonstrated to a homologous ‘R’ variant and an ‘M’ variant.

Although it is possible to produce immunity in animals with dead trypanosomes further studies, particularly in the field, are necessary to find its practical application.

Six new species of cestodes from birds have been described. These are: Ophryocotyle indicus from the Rufous Babbler, Turdoides subrufus; Biuterina dicruri from the Grey Drongo, Dicrurus leucophaeus longicaudatus; Choanotaenia tandani from the Himalayan Whistling Thrush, Myiophoneus caeruleus temminckii; Choanotaenia picusi from the Scalybellied Green Woodpecker, Picus squamatus; Panuwa stylicirrosa from the Little Scalybellied Green Woodpecker, Picus xanthopygaeus; and Anoncotaenia indica from the Rufous-bellied Niltava, Muscicapa sundara.

Extensive cross-reactions have been found between cultural forms of trypanosomes of the ‘brucei’ group by the agglutination reaction. The antigen (or antigens) responsible for agglutination are apparently specific to the ‘brucei’ group of trypanosomes. These antigens are also quite stable to the presence of specific antiserum in contrast to the serotype of the blood trypanosomes which are known to be altered in the presence of specific antiserum.

1. A local population of Gammarus pulex, infected with Heliospora longissima and Rotundula gammari, was found to have an intracellular developmental stage.

2. Experimental infections of G. pulex were made with the two species of gregarines. In the case of R. gammari infections, large numbers of intracellular developmental stages were found.

3. The taxonomic relationship of the genera Cephaloidophora and Rotundula is discussed.

Thanks are due to Dr P. Tate for constant encouragement and guidance during the course of this work and for the many helpful suggestions in the preparation of the manuscript. Thanks are also due to Mr D. W. T. Crompton for kindly giving me the infected material. The work was completed during the tenure of a Royal Society and Nuffield Foundation Commonwealth Bursary.

Evidence is presented of a periodicity of oogenesis and spermatogenesis in D. aegira. Pauses in oogenesis were detected between successions of oogonial divisions; in spermatogenesis, the intervals appeared to be longer and the pauses came before division of primary spermatocytes. Regulation of division rates was such that between two and three times as many spermatozoa as oocytes were produced.

Observations indicated that spermatozoa emerged from the axial cell soon after their formation and made contact with oocytes early, often before these were fully grown. Properties of the oocyte cell membrane evidently precluded precocious sperm entry and the penetration of more than one spermatozoon.

Sincere thanks are due to Dr R. B. Short, who kindly made available all the material, and to Dr S. W. Fox and Dr C. B. Metz for the excellent facilities provided. This work was supported by P. H. S. Research Grant E 4749 (Institute of Allergy and Infectious Diseases) awarded to R. B. Short, and by N.A.S.A. Grant NsG–173–62 and N.S.F. Grant G–9150. Contribution No. 019 of the Institute for Space Biosciences.