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.

A large collection of avian Ascaridia from a wide diversity of hosts and localities is reported upon. It comprised six species, A. galli, A. columbae, A. compar, A. cristata, A. hermaphrodita and A. numidae. Their morphology is examined critically with reference to previous descriptions, especially in the case of A. columbae, A. cristata, A. hermaphrodita and A. compar, and a new variety of A. columbae is described.

The taxonomic significance of spicule morphology and the tubercles on the ventral surface of the male tail in Ascaridia is discussed.

A comparative study has been made of certain species of Diphyllobothrium which are primarily parasites of birds, but which have been obtained from man and other hosts, both naturally and experimentally. As a result of this work it appears that only two valid species are known in birds, namely: Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825). These species differ markedly from each other in certain morphological features and there appears to be a noticeable difference in their host-adaptation, inasmuch as D. ditremum occurs only in birds belonging to the families Phalacrocoracidae, Ardeidae, Colymbidae and Anatidae, while D. dendriticum occurs naturally in birds belonging to the Laridae and other families, and experimentally also in mammals.

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.

Measurements of 500 eggs respectively of S. bovis, S. mattheei and S. haematobium were made. These measurements included length, maximum breadth, and breadth at a point 50 microns from the non-spiked end of the egg. Statistical analysis of the results shows that it is possible, to differentiate between the three groups of eggs.

Reasons are adduced for suggesting that the statement that S. mattheei cannot infect man is not well founded; the question is under active investigation by the author.

The genera Galactosomum, Microlistrum and Stictodora are compared, and, while the first two are undoubtedly synonymous, the last is considered to be distinct.

The adult of the type-species of Galactosomum, G. lacteum, is fully described for the first time from European cormorants, and G. phalacrocoracis is regarded as a synonym.

A new species, Galactosomum fregatae, is described from the frigate-bird Fregata magnificens rothschildi.

The characters of all the species that have been assigned to Galactosomum are briefly defined, and a provisional differential key is given.

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.

Fifteen lots of fifty individual cysts from three separate batches were exposed to the action of potato root diffusate, the hatching allowed to continue to completion and the total larvae liberated from each cyst were counted. The data obtained were analysed both as they stood and after three different transformations for variability, as well as for independence between mean and variance. Very high variability corresponding to a coefficient of variation of 1.00 was detected, and there was, moreover, a very significant correlation between mean and variance. The most suitable transformations appeared to be either logarithmic or angular—the latter being probably the more useful. The latter, moreover, tended to increase the sensitivity of analysis. The importance of residual counts when hatching is complete is emphasized even in the absence of an angular transformation of the data.

The stem eelworm Anguillulina dipsaci (Kühn) Gerv. & v. Ben., is responsible for disease in numerous plants, amongst which are teazle, Dipsacus fullonum L., the type host and red clover, Trifolium pratense L. In both cases seed harvested from infected plants will often be infected by the stem eelworm in spite of the greatest care in dressing the seed.

Kühn (1857) in describing the parasite for the first time said:— The seeds of the diseased teazles differ from those of the healthy ones. They are not half so large nor so sharply angular. Whilst the pappus of the healthy seed is stalked that of the diseased seed is sessile and almost twice as large. The worms do not completely fill the diseased seed but occur within the atrophied ovule and also as small clumps of worms within the tissue of the abnormally thickened seed coat. The worms are found not only within the diseased seeds but in all other parts of the head including the pith where they cause not only abnormal growth but death and brown discolouration of the tissues.

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.

The lack of a rapid and reliable method of making permanent preparations of nematodes is most strongly felt in the case of the plant-parasitic forms. The method in general use for most plant- and soil-inhabiting nematodes consists in relaxing the worms by gentle heat, fixing in 5% formalin or Ditlivsen's fixative (Thorne, 1925) and then impregnating slowly with glycerine. This procedure is quite reliable for the non-plant-parasitic forms but its results with plant-parasitic worms are very uncertain. With the latter it is necessary to transfer from fixative to very dilute glycerine, usually 1.5% glycerine in 7.5% alcohol with a trace of thymol or copper sulphate to discourage moulds. The glycerine is allowed to concentrate very slowly during at least four weeks until the worms can be transferred to pure glycerine in which they are mounted. Even then the results are often disappointing for the worms very frequently collapse.

In considering this general problem recently the authors called to mind the appearance of worms stained within plant tissues by the acid fuchsin-lactophenol method (Goodey, 1987: Franklin, 1949). This method causes no collapse or distortion of the worms and takes but a few minutes from living material to permanently stained preparations. The process has now been developed for use with free specimens of Anguillulina dipsaci and plant-parasitic species of Aphelenchoides, and is as follows:

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).

This paper describes some hitherto unrecorded aspects of trematode development in a molluscan host.

It is shown that the rate of development of Fasciola hepatica in its host Limnaea truncatula is influenced not only by temperature but by the amount of food assimilated by the snail and by the number of rediae which are in competition within a single host.

The most rapid development of the parasite will occur in hosts which have access to ample supplies of food and in which moderate numbers of rediae become established. At laboratory temperatures, infection with a single miracidium rarely leads to the establishment of more than 40 rediae, a number which is apparently adjusted to the economy of the host, since it allows development at a maximum rate.

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.