Endolimax blattae, a small amoeba living in the cockroach hind gut, was cultivated in vitro for the first time.

Growth and encystment took place in diphasic serum-saline media with or without the addition of starch.

E. blattae grew well at 25 and 37°C. At the latter temperature the flagellates and Blastocystis which contaminated recently isolated strains were eliminated.

More amoebae and cysts were produced in cultures supplied with starch than in those without starch, and there seemed to be a relationship between depletion of starch and onset of encystment.

The results are discussed with reference to conditions in the natural environment.

I wish to express my thanks to Professor H. P. Moon, in whose department this work was carried out, for his help and advice, to my supervisor Dr Marjorie G. Guthrie for her advice, encouragement and constructive criticism, and to Dr Ann Bishop, F.R.S., and Dr Elspeth W. McConnachie for their invaluable advice on in vitro cultivation.

Some morphological characteristics of Cephalochlamys namaquensis from Xenopus muelleri collected at Kajansi, Kampala, are described.

Specimens of cestodes from other localities in Africa are compared with those from Kajansi in order to assess the reliability of the characters of the proposed genus Pseudocephalochlamys Yamaguti, 1959. Reasons are given for rejecting the genus.

The embryonated, non-operculate egg capsules hatch at once in water. The ciliated coracidium is eaten by cyclopid copepods and the oncosphere rapidly penetrates through the mid-gut wall into the haemocoel. The procercoid develops a cercomer which moves actively during development and which retains the six hooks of the oncosphere. The procercoid develops the scolex, osmoregulatory canals and calcareous corpuscles typical of the adult while within the copepod. It is enclosed within a membrane. The procercoid is infective to Xenopus toads 20 days after being ingested by the copepod. No other intermediate host has been found.

Thermocyclops infrequens Kiefer is the intermediate host at Kajansi, Kampala. The maximum number of C. namaquensis recovered from one toad was 103; usually there are between 1 and 6 per toad. Between 22% and 100% of Xenopus muelleri and X. laevis from different localities are infected with C. namaquensis.

I wish to express by thanks to the Fisheries Officers and fishermen of Kajansi Fish Farm who have willingly caught Xenopus for me whenever required, and also to the many other people who have assisted me in getting specimens with which to work.

I am also indebted to Mr L. Rugema who prepared most of the histological preparations, to Dr J. Green, Westfield College, London, who kindly identified Thermocyclops infrequens, and to Dr G. Rees, University College of Wales, Aberystwyth, who gave me many useful comments during the course of this work.

A research grant from Makerere University College contributed towards the cost of obtaining specimens.