Malaria is endemic over a wide area of the earth's surface. Although popularly associated with tropical or subtropical countries, it occurs as far north as the south of Sweden and Lake Ladoga in Russia and as far south as Bechuanaland, Swaziland and Natal in South Africa and the Argentine in South America. Though most frequent in low-lying districts it may be found at altitudes as great as 6000–9000 ft.

Our knowledge of this interesting group of mites has been built up by the writings of some twenty-two acarologists, of different nationalities, whose papers are published in some four or five languages and have appeared in thirty to forty journals.

Two vivax-like parasites, believed to be true P. vivax but in abnormal form, are described. The deviation from normal appearances was probably due, it is suggested, to growth in an abnormal environment.

The developmental stages of Braula coeca are described. The larva is an inquiline living in a tubular burrow which it makes by mining on the inner side of the capping of the honey cells in the comb of the hive bee. It is meta-pneustic and bears characteristic anterior and posterior girdles of sensoria.

The pupa is apparently unique among Cyclorrhapha in that it is enclosed within the unmodified cuticle of the 3rd instar larva, no puparium being formed. It is suggested that this feature is a degenerative change owing to the cessation of a particular phase of hormone activity.

The similarity of form and structure shown by the larvae of Braula and of the Chamaemyiidae (Ochthiphilidae) is indicative of a fundamentally close relationship. Their imagines on the other hand have undergone widely divergent evolution.

During the last few years I have successfully used a new method for investigating intestinal amoebae in cultures, and in the hope that it may also prove serviceable to other workers I now propose to describe it. At the same time I take the opportunity of noting two new staining methods which I have used especially in conjunction with this technique, but which are of general utility in protozoology and cytology.

1. Experiments are described in which various concentrations of pyrethrum in oil are tested for speed of stimulation of Ornithodorus larvae. There is a logarithmic relation between concentration and speed of stimulation, except with concentrated solutions (stronger than 0·015% by weight of pyrethrin I) in which there is a relative retardation of response.

2. As larvae grow older they respond more slowly, and this is probably due to an increase in thickness of the cuticle in natural growth.

3. Mineral oils induce much swifter penetration of the pyrethrum than any of the vegetable oils tested.

My thanks are due to Prof. Buxton in whose department the work was done, and also, to Dr J. T. Martin of Rothamsted Experimental Station, who kindly analysed samples of Pyremist ‘L’ for pyrethrin I.

Members of the genus Trichuris Roederer, 1761 (Syn. Trichocephalos Goeze, 1782; Trichocephalus Schrank, 1788) have a characteristic shape. The oesophageal portion of the body is very slender and is longer than the posterior portion, the latter being usually much stouter than the former. The eggs are lemon-shaped with a knob at each end, while the egg-shell is of a dark brown colour when seen in faeces.

The genus Lecithocladium was erected by Lühe in 1901, with L. excisum (Rud. 1819) as the type species. In addition to the type species, the genus contains L. excisiforme Cohn, 1902, L. gulosum Linton, 1910, L. longicaudum Shen, 1934, L. psenopsis, L. magnacetabulum and L. pagrosomi Yamaguti, 1934, and L. johnii Yamaguti, 1938. L. barbatum Cohn, 1902, has been transferred to the genus Dinurus Looss, 1907, and L. crenatum (Molin, 1859) is regarded by Looss as a ‘species inquirenda’, while Lühe maintains that it is synonymous with L. excisum. The author (1937) has added two more species from Indian hosts to the genus. These are more fully described in the present paper.

In the course of an extensive parasitological examination of Indian food fishes the author recovered, amongst others, six specimens of an interesting trematode from the gut of a fish examined at Karachi in June 1936. The trematode, though obviously belonging to the family Allocreadiidae, represents a new genus, Horatrema, and a new subfamily, Horatrematinae. This new genus forms a connecting link between Cymbephallus Linton, in Manter, 1934, and Parva-creadium Manter, 1940, of the subfamily Allocreadiinae, and the type genus Notoporus of the family Notoporidae Yamaguti, 1938. It will be appreciated from the systematic discussion at the end of the paper that the taxonomic status of the family Notoporidae is untenable, and it is, therefore, reduced to the rank of a subfamily, Notoporinae, under the family Allocreadiidae. Further, in view of the presence of a cirrus-sac in Notoporus trachuri Yamaguti, 1938, it has been considered necessary to assign it to a new genus, Neonotoporus