A survey of the incidence and distribution of Onchocerca volvulus in Nyanza Province was carried out by the “skin-snip” method of determining the presence of microfilariae in the skin. 5,842 Africans were examined.

An account is given of the incidence of the infection in five different foci, with some observations on ocular complications, cutaneous nodules, abnormal skin, and age and sex incidence.

The survey disclosed one hitherto unrecorded focus of the infection, namely, at Riana in South Kavirondo District and confirmed the existence of another on parts of the Kuja River in the same district. The endemic focus discovered in Lumbwa District by Dry in 1921 was surveyed for the first time.

Each focus is fairly well circumscribed and all are. situated at an altitude roughly defined by the 5,000′ and 6,000′ contour lines. Both of these limitations are determined by topography and by the insect vector, Simulium neavei, whose habits confine it to a certaintype of environment. This is characterized by the presence of fastrunning rivers or streams; a hilly or mountainous terrain; well-wooded river banks.

Hadjelia truncata, Hadjelia inermis and Viguiera euryoptera are newly recorded from India.

Quasithelazia tenuis is described in detail and the genus Quasithelazia Maplestone is considered to be a synonym of the genus Schistorophus Railliet, 1916.

Microtetrameres inermis is newly recorded from India and is described from two new hosts, Temenuchus pagodarum and Brachypternus bengalensis.

Physaloptera alata is described from the type-host, Accipiter nisus.

Syphaciella indica is described in detail and compared with the original description.

Buckleyfilaria buckleyi n.g., n.sp., is described in detail and the new genus is compared with the related genera of Aproctinae.

A new species of Aproctinae is described and assigned to the genus Eufilaria with a slight modification of the generic definition.

Lerouxinema lerouxi n.g., n.sp., is described from the heart of Galloperdix spadicea and its relationship with other genera is discussed.

A new species of Splendidofilaria is described and compared with the two other species of the genus.

Squamofilaria coronata from the Indian Roller is described fully and compared with earlier descriptions of the species.

Diplotriaena tricuspis is recorded from a new host, Lanius vittatus.

A new species of the genus Avioserpens is described from Ardeola grayii.

Field and laboratory observations confirm that L. truncatula is an amphibious species, living in temporary pools and muddy places which often become dry for part of the year.

During times of drought the snail survives in a state of aestivation. At the laboratory newly hatched snails are able to withstand at least two months' aestivation while older snails have been demonstrated to remain alive for more than a year; considerably longer than suggested by previous workers.

Capillaria cadovulvata was first described in 1945 by Madsen who found that it occurred commonly in the caeca of adult pheasants, and occasionally among partridges in Denmark. It is recorded now from a grey partridge Perdix perdix in England, where it had set up pathological changes which had been the cause of death. Madsen does not mention the presence of any lesions in association with this parasite. Though this is the first record of the species in England, it may be more common, for the species of Capillaria are not always easy to differentiate without recourse to fairly high magnification. In view of this, and because of its pathogenic nature, it seems worth while recording its occurrence and the lesions that may follow its presence.

Twenty-eight cases of adult or larval worms belonging to the genus Gnathostoma Owen, 1886, have been recorded from man.

One of the earliest records is from Malaya where Samy (1918) extracted a larval gnathostome from the finger of a young male Chinese.

Taking into consideration the whole of this experiment, as reported in this and the two preceding papers, the following are the salient conclusions.

1. Of the various plant criteria tested, the height of plants at about the 45th day after planting, and the weight of all tubers produced, are the two most useful criteria. Eelworm criteria are conveniently analysed in logarithmic transformation.

2. In the first season the presence of numerous eysts of Heterodera rostochiensis had no detectable effects on the growth or yield of the potato plants. Plants grown in the same soil without further treatment in the second year both were shorter and produced a much smaller crop than the uninfected.

In the British Isles potatoes are subject to many pests and diseases of animal, fungal and virus origin. In the first class there are two different kinds of eelworms or nematodes which attack the plant, one affecting the roots and the other the tubers. The former is the cystforming species Heterodera rostochiensis and the latter was for many years considered to be a specialized race of the stem eelworm, Anguillulina dipsaci. As a result, however, of work carried out by Thorne (1945) in the U.S.A., it is now known to be a distinct species, Ditylenchus destructor. Though resembling A. dipsaci closely in size, general shape and structure, D. destructor differs from it in one or two points of microscopic detail which are constant and can be seen in suitably mounted specimens when examined under high magnification. The most important of these is the presence of 6 fine longitudinal lines or incisures on each side of the body in the area known as the lateral field as compared with 4 such lines in the case of A. dipsaci (fig. 1).

When the presence of nematodes in plant tissues is known or suspected it is often useful to be able to show the exact situation of the parasites and their biological condition, i.e. whether they are quiescent or active. If plant tissues are teased apart in water active nematodes will be freed and will soon be seen swimming in the water, or, if they are in a state of quiescence, and yet viable, they will revive in an hour or more and become active in the water. Whichever is the case, there may occasionally be some doubt as to whether the nematodes were really in the tissues of the plant or were carried on the outside. The larvae and eggs of most parasitic eelworms are so small that they may easily be overlooked amongst the teased plant tissue, with which there may also be numbers of detached plant hairs closely resembling nematodes in their shape, size and transparency. If the parts of the plants likely to contain eelworms can be stained so that the worms take up the stain in contrast to the plant tissue, and can be seen in their natural position, a much more accurate picture of the situation may often be obtained than that derived from teasing the tissues in water.