1. Eubothrium crassum (Bloch) is re-described with additional information about the scolex and genitalia.

2. Specific differences between E. crassum and E. salvelini are commented upon and figured.

3. The second portion of the uterine duct lying between the central chamber of Mehlis's gland and the uterine sac is established as the “fertilization chamber”.

4. Polar bodies and maturation divisions are described and figured in definite relationships with the ovum as evidence of normal maturation in a cestode.

5. The position of the receptaculum seminis is determined and a new name, the “vagina sac”, is given to what was previously described as a receptaculum seminis. It is thought to serve for propulsion of male and female cells into the uterine duct.

A number of helminths from a small bat from a cave in Northern Rhodesia were presented by Dr. P. L. leRoux to the author for study. The collection of consisted of about twenty specimens of one species of trematode, Prosthodendrium cordiforme; the rest were nematodes, namely, two males and three females of Molinostrongylus pseudornatus sp. nov., at least one species of filarial worm, one species of Capillaria and one or two species of trichostrongylid nematodes. Only the first two helminth species mentioned above were studied in detail. The others, for one reason or another, were inadequate for detailed study.

The description of this species is made from two males and one female specimen. They were collected from the intestine of the Homa fish from the Kafue River, Mazabuka, Northern Rhodesia by Dr. P. L. leRoux.

A method is described for the recovery of Oxyurid nematodes from faeces and ingesta of mice, by washing and sieving after the worms have been stained with iodine. It can be performed in one quarter of the time and is more efficient and less fatiguing than the method previously employed.

Two methods of setting up axenic cultures of several species of Rhabditinae are described. Both methods depend on the killing and superficial sterilisation of gravid females with a chemcal steriliising agent, and their transferance to an innocuous medium containing antibiotics. The young worms which hatch from the eggs contained in the dead female worms are then collected aseptically. In one method merthiolate is used as a sterilising agent and in the other hydrogen peroxide.

The effectiveness of both methods in freeing the young worms from contaminating micro-organisms has been evaluated by inoculating standard bacteriological culture media with the worms.

Starting with such young worms, bacteria-free cultures have been set up using media previously described by Dougherty and his coworkers for the cultivation of free-living nematodes.

An inverse relationship has been demonstrated between egg counts and antibody titres. This relationship is also evident on a seasonal basis in the “spring rise”.

The “spring rise” is preceded by a decrease in the immune status of the sheep and is terminated by a self cure mechanism which establishes a period of protection.

The significance of these findings is discussed with regard to the onset and development of the “spring rise”.

A thermostable serum constituent is described which has a lethal effect on the miracidia of F. hepatica. This requires the thermolabile components of guineapig complement for its lethal action. It is apparently similar to substances present in other normal sera and which have an antagonistic action on a wide range of organisms. The mode of action is discussed.

An examination of the type material of Dibothriocephalus medius Fahmy, 1954, was made possible by the kind co-operation of Professor Swann of the Zoology Dept., Universityof Edinburgh, where the specimens are lodged.

In the Summer of 1943 Dr. P. L. leRoux, to whom I am very grateful for the material, madea collection of worm parasites of ducks and waterbirds, shot near the Kalunga River, Chunga Farm, Chinsali District, Northern Rhodesia. Three genera of Trematodes are represented in this material, two of which, as far as records show, viz. Typhlocoelum and Paryphostomum, whose members are widely distributed in Asia, Europe and America, are here recorded for the first time from the African Continent. Petasiger variospinosus is recorded from a new host and a new locality.

This paper is devoted to a critical analysis and revision of the systematics of the trematode genus Opisthorchis. It is shown that there is no justification for the recognition of the genera Amphimerus Barker, 1911, Notaulus Skrjabin, 1913, Gomtia Thapar, 1930, Evranorchis Skrjabin, 1944 and Euamphimerus Yamaguti, 1941.

The generic diagnosis of the genus Opisthorchis has been amplified, and on the basis of the information available in the literature mainly, certain species in this genus are suggested to be synonyms of earlier recorded forms. A list is presented of the species recognized and the host or hosts are indicated as far as is possible.

Opisthorchis geminus is recorded from two new hosts, Plectropterus gambensis and Dendrocygna viduata.