The material of the species to be described was found in a small collection of parasites from Zanzibar, placed at my disposal by Professor G. H. F. Nuttall, F.R.S., to whom I wish to express my thanks. As only a few cestodes have hitherto been recorded from East Africa and its helminth fauna is therefore largely unknown, a list of the forms identified is given at the end of the paper. I desire to acknowledge my indebtedness to the Birmingham Natural History and Philosophical Society for a grant towards the expense of preparing the plates, both in this and the preceding paper (Parasitology, XIII. No. 1, March 1921, p. 1).

1. Cercaria pekinensis, a new cystocercous cercaria, is described.

2. The excretory system of the developed cercaria consists of a bladder, a drainage channel through the tail and a pair of anterior collecting tubules, each of which receives eight main (tertiary) branches. Each branch is composed of 2 × 4 × 4 units. The posterior-most branch cares for the drainage of the tail, including the corresponding flapper.

3. A study of representative stages in development shows that the common denominator of the excretory system is α + β, while the pattern of the developed cercaria is expressed by 4 (α)2 + 4 (β)2.

4. The fundamental pattern of tie cercaria is likewise found in the sporocyst.

5. These data have a significant bearing on the application of mathematics to the problems of growth and development.

A Batch of twenty-nine larvae of Stegomyia scutellaris Walker, were collected on 24 July 1920 from an old earthenware pot found in a Malay's garden. It was at once seen, even with the unaided eye, that many, some considerably paler than others, were characterised by a pearly-white opalescence of the tracheal gills at the hinder end of the body.

The material which forms the subject of this communication was derived from Dr W. A. Lamborn's collection, and was placed at my disposal through the kindness of Dr Guy A. K. Marshall, Director of the Imperial Bureau of Entomology, London. It comprised eight larvae of Stegomyia scutellaris Walker, which had been preserved in formaldehyde solution (10 per cent.), and the specimens were mounted individually on microscope slides in the same medium.

Among six parasitised larve of Stegomya scutellaris Walker, collected by Dr W. A. Lamborn in the Federated Malay States, Five Contained a ciliate which I have described(Parasitology, XIII. p.216)under the name of Lambornella stegomyiae n.g., n.sp., while the remaining larva harboured a new parasitic fungus which forms the subject of this communication. The larva had been fixed and was preserved in formaldehyde solution (10 per cent.) and was labelled: “Larva of Stegomyia scutellaris Walker. Infestation with protozoal parasite and a luxuriant growth of Vorticella. Kajang,” by Dr Lamborn. When the larva was examined under a low power the surface of its body was found to be extensively covered with tufts of Vorticella, whilst its interior harboured an enormous number of parasites which in the gills and the posterior segments were packed in solid masses completely filling these parts (Fig. 1). As seen by transparency the parasites are oval in shape, 37·5 to 57 μ long and 20 to 30 μ in diameter, surrounded by a more or less thick yellowish wall. In their external appearance, size, and position in the host, they are so surprisingly similar to Lambornella that it was at first quite natural to take them for the resting stages or cysts of this ciliate.

The protozoa found in the intestines of termites constitute one of the most interesting but less illuminated fields in protozoology. The amount of work done by a number of authors in several different parts of the world is, however, already fairly large, especially valuable papers having appeared in recent years, so that some light has been thrown on the field. Nevertheless, important questions regarding morphology, physiology, systematics, etc., still remain either insufficiently studied or almost untouched. Having myself been occupied for some years past with these interesting organisms, harboured by three species of termites in Japan proper and Formosa, and having made observations which seem to be of some interest, I propose in this paper to describe the chief results of my studies.