In several previous publications by the present writer reference has been made to the relation between the root excretions of plants and the bionomics of the eelworm Heterodera schachtii. Amongst these is a short preliminary note on the significance of the root excretions of certain grasses as a possible means of controlling the nematode. The experiments referred to in this paper having been continued and extended, and the favourable results of the first year's field work having been maintained, a more detailed account of the researches seems to be justified, although the field experiments are still in progress and many aspects of the problem which require laboratory investigation are as yet comparatively untouched. As previously indicated, of the two main lines, chemical and biological, along which investigations must be pursued for a full understanding of the relationship between the reactions of the nematode and the stimulus of the root excretions, the chemical is the more fundamental, and until further work has been carried out from this standpoint much of the biological work is necessarily of an empirical character. It is, however, on purely biological lines that the greatest progress has so far been achieved, and it is with this side of the work solely that the present paper deals.

In the spring of 1932 an experiment was set up to observe the effects of intensive grazing, by the heavy stocking of a pasture, on the worm infestation of animals, and to arrive at some estimation of the consequences of modern grazing practices. These observations covered a period of one year and the results obtained from the experiment, which was carried out by one of us, have been put forward in an earlier paper (Morgan, 1933). Some conclusions were drawn from the work but these were considered as purely provisional owing to the small scale of the experiment and to the observations covering the comparatively short period of a year. It was pointed out that the effects of overstocking would not become evident until pastures had been under a system of rotational grazing for many seasons and when the concentration of helminth ova and larvae had reached a very high level. With this in mind it was decided to proceed with observations on the effects of heavy stocking on the worm burden by setting up a fresh experiment running on lines similar to that already described but using, in places of the goats in the 1932–33 work, one-year old sheep, as it was thought that this type of stock would ensure a closer cropping on the experimental plots.

In the literature which deals with the gape-worm, Syngamus trachea, found commonly in England, its presence has been recorded from a fair variety of birds. It has been found several times in the starling—Nathusius (1837), Megnin (1883) and, among others, by Lewis (1925). Dujardin records having found it in the magpie, Corvus pica, (1845) Megnin (1883) found it in the swift (cypselus apus), green woodpecker (Picus viridis), black stork (Ciconia nigra) and in the pheasant and partridge. It has further been recovered by Lewis (1925) from the rook (Corvus frugilegus), thrush (Turdus musicus) and jay (Garrulus glandarius), while in the Ministry of Agriculture Leaflet No. 58, the sparrow and linnet are also cited as being occasional hosts, and Walker (1886) has found it in the robin. The present writers have found a closely related species, S. merulae (Baylis, 1926) in the tracheae of four blackbirds which came into the laboratory during the summer. Though these birds seem to be only occasional hosts, most of the authors stating that the infections occurred only in young birds while the adults are comparatively free from this worm, yet a high percentage of young birds are frequently found to be carrying this parasite: for instance, Elton and Buckland (1928) in a batch of 33 young rooks obtained from the Oxford district, found 31 infected, while of 8 old birds only four were infected and these only lightly. Lewis in 1926 found 35 per cent. of a sample of starlings infected but he did not notice the age of the birds. Morgan examined two nests of young starlings and found that all of one batch harboured S. trachea. He suggests that they may have become infected from the earthworms brought in by the parent birds as food.

Amongst the plant-parasitic members of the genus Anguillulina, 12 species have been recorded from true galls and of these, one occurs on roots and the remainder on shoot structures. In four only of these species have we any detailed information on the structure of the galls formed as a result of the action of the parasite, namely in the cases of A. tritici, A. agrostis, A. graminophila and A. radicicola. In the case of the two first mentioned, galls are formed from modified flower tissues; in the case of A. graminophila we have galls on leaves and in A. radicicola galls on roots. There are considerable gaps in our knowledge of the reaction of the host plant to the particular parasite attacking it and also concerning the mode of action of the latter in stimulating the production of galls by the host.

More than twenty years ago Schwartz (1911) described a disease of cultivated violets associated with eelworm attack. The plants were obtained from gardens at Greiz and Kreuznach in Germany and in all cases had distinct gall-like swellings at the bases of the leaf-stalks. As the disease progressed the leaves became smaller and smaller and the leaf-stalks shorter until, finally, an irregular, walnut-sized gall was produced the surface of which was covered with abortive buds. Schwartz drew attention to the similarity presented by such plants to the “cauliflower” condition in strawberry plants associated with the presence of Aphelenchoides fragariae. Goffart (1930) mentioned the fact that the disease persisted for a time in Germany; being reported in 1910–12 and 1915–17 but had not been recorded again up to 1930.

There has recently been published a series of observations, based on experimental evidence, which goes to show that the course of an helmintic infestation may be significantly affected by the diet which is fed to the experimental animal. These results which have emanated mainly from Ackert and his colleagues (1929 and 1931) and from Foster & Cort (1931 and 1932), Hiraishi (1927 and 1928) and from Nagoya (1931) show that the vitamins are frequently significant factors affecting the development of Ascaridia, hookworms and Ascaris. In a later paper (1933), Ackert and others showed further that the type of amino-acids and the variety may also be factors influencing the development of Ascaridia lineata in chickens.

Experimental evidence of immunity to helminth parasites is on the whole very scanty. Several workers have drawn attention to the fact that immunity can be acquired as a result of age alone. Ransom (1921) using Syngamus trachealis in chickens, Herrick (1925) with Ascaridia lineata also in chickens, Sandground (1928) with Strongyloides and Nanophyes in dogs and cats, are three examples.

Twenty-five species of Nematode have been found to be present in sheep in Manawatu district. The species of greatest economic importance were found to be in most cases of importance in other temperate climates.

In the cases of certain species, saturation of Manawatu district has not yet occurred, e.g., in the cases of Cooperia oncophora, C. punctata and Ostertagia ostertagi.

The countries of origin of the foundation stock have limited the number of species. Most of the importations have been made from Britain and Australia.

As few nematodes of the sheep require intermediate hosts, their entrance to a new country, New Zealand, has not been prevented to any extent on this ground. Muellerius capillaris has been able to survive on account of the abundance of its normal host, which has been introduced also.

The climate of Manawatu is such that the extremes of summer and winter are not severe enough to exert complete control on the various species. Infective stages are well able to survive these less favourable periods. The climate is sufficiently equable to enable out of door pasturing throughout the year, so that in the cases of most species of nematoda infection it is possible also throughout the year.

The farming systems in vogue involve almost solely the use of permanent pasture which is mostly of high carrying capacity. This enables concentration of stock and in conjunction with continuous grazing throughout the year, enables the excessive multiplication of the various species of nematodes.

The prominence placed on the fat lamb industry means that much attention is devoted to the raising of a population susceptible to worm infection.

A prevailing practice is to introduce culls from the surrounding hill districts for purposes of fattening, and sheep from the Hawke's Bay district in time of drought. There is consequently a continual introduction of parasites in these animals.

Cattle are the chief reservoir hosts of nematodes of sheep in Manawatu district. These occur in large numbers in the district and frequently dairying is combined with sheep farming, so that they become important sources of infection to sheep in respect to some species of worm, e.g., Cooperia oncophora, C. punctata and Ostertagia ostertagi.

It would seem that the tendency in the district is towards the increasing of the carrying capacity of pasture. This should result in the multiplication of parasites, particularly Nematodes, to a greater extent than has been the case.

de Man (1880) described the species Tylenchus macrophallus, obtained from pasture soil, and in a later publication (1884) gave a fuller account of it with drawings. Reasons are given later in the present paper for the removal of this species to the genus Paratylenchus. Micoletzky (1921) established the genus Paratylenchus containing but one species, namely, P. bukowinensis, obtained from around grass roots near Czernowitz in Bukowina. The description was based on a single female specimen which was found only after mounting in glycerine. In spite of this, however, the distinctive characters of the genus were clearly indicated and are sufficiently marked to separate it from the nearly related genus Anguillulina. Cobb (1923) gave a detailed description of the anatomy of another species, also obtained from around grass roots, under the name of Paratylenchus nanus, which he considered might be synonymous with P. bukowinensis, and a brief account of an immature form which he called P. anceps but which very closely resembled his P. nanus. In the case of both of these forms only females were found.

A considerable amount of attention has been paid to the parasites of fresh water fishes in the West on account of the great economic importance of fishes, particularly their value in food. Their importance further increases, when we find that they also serve, in several cases, as carriers of the larval stages of the helminth parasites of man and domesticated animals. The work prior to 1924 has been summarised by Nicoll (1924), where he has given a complete bibliography on the subject, and has, besides, indicated the important and characteristic Trematodes of fresh water fishes. In this list he enumerates the forms like Sphaerostoma bramae (= Dist. globiporum); Allocreadium isoporum; Catoptroides macrocotyle; Azygia lucii; Bucephalus polymorphus; Diplostomum volvens; Diplozoon paradoxum; and Gyrodactylus elegans. This list has been considerably enlarged by subsequent workers by the addition of several general and species from the fresh water hosts from different parts of the world, the principal workers being Nicoll, Odhner, Poche and Travassos. In India, the additions to our knowledge of the Trematode parasites of fishes has been made by Southwell (1913), Southwell and Prashad (1919), Verma (1927) and Thapar (1930). The present paper adds yet another genus to the already extensive list of Trematode parasites of fishes.

The general outlines of the life history of Taenia pisiformis (Bloch 1780) in the dog and the rabbit have long been well known. The following reinvestigation of the early stages of the development of Cysticercus pisiformis in experimental rabbits was undertaken with the primary objective of checking or refuting the “division” of the Cysticercus described by Moniez in his classical monograph on the Cysticerci, published in 1880.

This paper embodies certain experiments on control of the nematode Aphelenchoides ritzema-bosi Schwartz, 1911, on chrysanthemums, and were started in September 1930 at the request of several commercial chrysanthemum growers in Staffordshire and Warwickshire.

1. A new species of Syngamus from the pharynx and nares of domestic cats in Trinidad is described.

2. The larval development from egg to 3rd stage larva is described with particular reference to the anatomy of the 3rd stage larva.

3. An attempt to trace the life cycle of the worm by direct infection of cats with the 3rd stage larvae was unsuccessful. It is suggested that an intermediate host is essential in the life cycle of this species.

It has been generally held that the severe anaemia and other pathogenic effects of infestation by hookworm in man and dogs, and by Haemonchus contortus in sheep, are insufficiently explained by the amount of blood removed by the parasites. The action of haemotoxins has therefore been postulated.

The present work forms a continuation of a survey undertaken three years ago, with a view to elucidating the nemic parasites commonly found in fishes of Canadian waters. These species have proved to be largely undescribed, and old species have always offered some new points of interest. The greatest difficulty has been encountered with the literature, much of which was difficult of access. Only those papers which have a definite bearing on the forms studied, and convey some pertinent information, are included in the appended bibliography.

It is only within the last few years that the various species of Bulbous Irises have been recognised as host of Anguillulina dipsaci. Despite the comparative paucity of information on the matter there is evidence of the likelihood of infestations becoming serious in the immediate future. It may, therefore, be of value to place on record such information as is at present available.

Four lambs introduced to infective pasture early in life acquired an immunity to parasitic gastritis, the immunity being sufficiently strong to maintain them in good health under conditions of repeated reinfestation, heavy enough to lead to the death of ten lambs of a like age, but not so protected, within periods varying from weeks to weeks. At post-mortem examination the protected lambs were found to carry more worms than many of the lambs which died, although they had been observed to disseminate only one-thirteenth the number of eggs of some of those fatally affected. The infestation of individual lambs in the various groups showed marked differences, amounting in some instances to the presence of a large number of worms of one species in some lambs and the total absence of worms of that species from others.

The observations lead to the following conclusions:—

1. Lambs are able to acquire an immunity against parasitic gastritis powerful enough to protect them against a rate of reinfection at pasture that is sufficiently great to result in the death of unprotected lambs in less than seven weeks.

2. This immunity operates against the acquiring of infection, but also in enabling the lambs to resist the injurious effects of the infection. Resistant animals may carry more parasites than are carried at the time of death by non-resistant animals.

3. The immunity is acquired slowly and does not appear to become firmly established for 18 weeks. A gradually acquired infection leads to immunity while a quickly acquired infection leads to death where the final number of parasites is the same in both instances.

4. The immunity is specific and operates more powerfully on N. fillicolis and H. contortus than on Ostertagia, Trichostrongylus and Cooperia.

5. The immunity has an inhibitory influence on egg laying and on the development of young worms; the egg output of the worms may be reduced to one-thirteenth of the normal.

6. There are marked differences in the reactions of individual lambs, instances of marked resistance and of marked susceptibility having been observed.

7. The symptoms of parasitic gastritis are due to something more than the abstraction of blood by the worm.

8. The part of immunity which inhibits the production of eggs by the parasites develops earlier than the resistance to the harmful effects of the infestation.

1. The life-cycle of Filaria ozzardi was studied in St. Vincent, B.W.I.

2. Culicoides furens Poey, a common sandfly in Calliaqua, where a 37·7% human infection was found, was used in the experimental infections.

3. Two hundred sand-flies, collected at Calliaqua, were given an infective feed of blood of F. ozzardi carriers. Of these flies, fifty-five, i.e., 27·5%, were subsequently found to be infected with developing stages of the parasite. The ingested microfilariae migrated within 24 hours to the thorax, where the entire morphological development takes place. In flies which were kept alive for seven or eight days, advanced stages were found in the thorax and head, and their emergence from the proboscis was induced by slight pressure on the head.

4. The development in the sandfly consists of a metamorphosis from the 1st stage or “sausage” larva to a 2nd stage larva during the first 3 to 4 days, and from this stage to a 3rd stage or infective larva on the fifth or sixth day. Two ecdyses occur during these metamorphoses, which are discussed in relation to the other human filarial parasites.

5. Five per cent. of C. furens caught at Calliaqua were found to be naturally infected with developing larvae, apparently F. ozzardi.

6. The possibility that C. paraensis, another species in Calliaqua, may also act as a vector, is not excluded.

Yakusu lies on the North bank of the river Congo twelve miles below Stanleyville and the termination of the rapids of Stanley Falls. One of largest tributaries, the Lindi, joins the main stream just above the settlement.

The question of helminth parasitism in British goats appears to have had little or no attention paid to it. This is somewhat surprising when one considers the fairly large number of goats which must be present in this country and, although no annual statistics as to the number of goats in Britain are available, Holmes Pegler (1929) observes that early in 1925 the Ministry of Agriculture, assisted by the British Goat Society, obtained returns of the number of goats in England and Wales which was set down as, roughly, 60,000. Similarly little definite data is available on the frequency and intensity with which these animals are infected by helminths in different localities. In this paper an attempt is made to supplement the meagre data relative to these conditions.