Schistosoma mansoni developing in mouse hosts subjected to frequent, heavy doses of stilbestrol show five effects: their normal survival rate is much reduced; the parasites for the most part remain in the liver past the time at which they normally migrate to mesenteric veins; both sexes develop to sexual maturity more slowly, if at all; a high proportion of the males have accessory gonadal tissue which probably is mainly ovarian; and the male worms average less than two-thirds as long as controls.

Two new species of Gymnocephalous cercariae are described from London. Cercariae lophocerca Fil. is recorded for the first time from Britain. A description of this cercaria is given.

A species of Trichuris is described from domestic cats in the Bahama Islands, and identified as T. campanula. Previous descriptions of the two species of Trichuris in the domestic cat are summarised, and it is concluded that both are valid species.

Most of our knowledge concerning the larval stages of the Strigeida is based on the studies of Canadian, American and European workers. One of the earliest descriptions of furcocercariae from British freshwaters was by Brown (1926, 1931) who recorded six new species from Cheshire. Later, Harper (1929) described three species and Hesse (1923) one un-named species, all from Scotland. During this period Matheson (1930) recorded the presence of Cercaria pseiidocellata Szidat, 1942 in an artificial lake at Roath Park, Cardiff, after reports of dermatitis from bathers. In 1932 Rees, during a general survey of Glamorgan, recorded an additional two species from the lake. These furcocercarial species were Cercaria X Baylis, 1930 and C. macrosoma which had been previously described by Brown in 1926.

1. Of 40 adult toads, Bufo marinus L., collected from 4 parishes of the Bermuda Islands, 82–5 per cent were infected with the lung worm Rhabdias sphaerocephala Goodey. The average number of worms per infected animal was 10 and the largest number recovered from a single toad was 50.

2. Although some eggs hatch in the lower rectum and cloaca, most do not hatch until they are evacuated and are lying in or on the fresh faecal material on the ground.

The neotenic adult resembles the normal adult in general form, but is considerably smaller, varying between 1·4 and 3·5 mm. in length. The caudal disc bears three pairs of suckers, incompletely developed anchor hooks, and infrequently, persistent larval booklets (Fig. 7, l.h.).

Fine brown granules colour the intestine, and anteriorly four pigment spots mark the eyes. The gonopore (Fig. 7, gon.) is posteriorly placed, lying some distance behind the transverse level of the excretory openings. Vaginal prominences and copulation pores are absent.

It has been shown that guineapigs can be effectively protected against re-infection by the subcutaneous inoculation of embryonated Ascaris eggs (Soulsby, 1957). The purpose of this communication is to report a successful attempt to immunize guineapigs against a lethal oral challenge dose of eggs by the intravenous inoculation of third stage larvae of A. suum.

Three groups, each containing nine guineapigs, were infected with Ascaris as follows: Group I was given 10,000 eggs by mouth. Group II Was inoculated intravenously with 2,000 third stage Ascaris larvae which had been obtained from the lungs of other guineapigs on the sixth day of infection. Both groups were challenged at the same time with 250,000 eggs by mouth, along with a control group (Group III) which had no previous infection. The guineapigs in Group I were re-infected after 18 days and those in Group II after 12 days.

The number of cysts used for each replicate in a dilution hatching trial may be reduced to 10. Log. total hatch is used, instead of total hatch itself, and the mean for each dilution determined from the log. values; the logs, of these means, plotted against dilution in the usual way, gives a straight line as in the original Fenwick technique. Reduction of the number of cysts permits the use of commercially available utensils to form an easily handled set-up.

A number of male and female specimens were available for study. They were collected by my colleague Mr. J. McClelland who very kindly made them available for study.

Description: The worm is very small with the largest diameter at the cephalic end and tapers down posteriorly and rather markedly so in the female worm (Fig. 4). The cuticle has fine striations. The bivalve buccal capsule has a number of longitudinal ridges of varying lengths. The number of these ridges are different for the male and female. The head is slightly tilted ventrad. There is a pair of tridents. The ventral trident is small and indistinctly branched. The dorsal trident is large and clearly trifid. The posterior part of the buccal capsule ends in six small projections (Fig. 1).

Through the courtesy of Drs. C. Kulasiri and C. H. Fernando this fine collection of camallanid nematodes from freshwater fishes in Ceylon was placed at my disposal for study.

Camallanid nematodes are rather confusing in a way as several species are often found within a single host. The study is further complicated when only a few specimens of a species of either sex are found. With an extensive collection, however, these nematodes are not troublesome.

The family Camallanidae is examined and two new subfamilies Procamallaninae and Camallaninae are erected for retaining the existing and new genera; the former subfamily for worms with a continuous buccal capsule and the latter for worms with a bivalve buccal capsule. The genus Camallanus s.l. is examined in detail and a revised definition given. Camallanus s.l. is divided into Camallanus s.s., Zeylanema Yeh, 1960, Piscilania gen. nov., and Serpinema gen. nov.

A number of these nematodes were sent to this Department for identification early in 1958 by Dr. J. F. B. Edeson from the Institute for Medical Research at Kuala Lumpur. The specimens were collected from the peritoneal cavity of Macaca irus. Since then, several further collections of the same species have been sent to this Department from time to time. The latter collections came from several laboratories using monkeys caught in Malaya and Siam for the production of poliomyelitis vaccines.

In 1956 the author described five new species of Procamallanus from India and also gave an amended key to the species, originally described by Annereaux (1946). Meanwhile a few more species were reported from India and elsewhere, but as the author had no access to the publications, these species were not included in the key. To clarify certain points the following review is given.

During the tour in Kashmir, two males and four females of the species to be described were collected from the vicinity of the heart and the body cavity of the white cheeked Bulbul, Molpastes leucogenys leucogenys.

These are rather slender worms with attenuated anterior ends. The posterior ends are twisted into 2–3 coils. The cuticle is thin, smooth, nonstriated, but richly furnished with bosses throughout the length of the body.