Previous experiments on the application of ferric oxide or of calcium cyanamide to “potato-sick” land were carried out at the Kirton Agricultural Institute. The results were reported by Hurst & Franklin (1937), and indicated that ferric oxide had no effect either on the yield of potatoes or on the hatching of H. schachtii larvae, but that calcium cyanamide showed promise and was worthy of further trial. Experiments with this chemical were, by the kind permission of Mr. J. C. Wallace, Principal of the Kirton Agricultural Institute, and with the co-operation of Mr. J. Wood, A.R.C.S., continued for a second year.

It was observed in laboratory experiments that the lethal action of dilute solutions of calcium cyanamide on the larvae of Heterodera schachtii was more rapid when these solutions were rendered slightly acid. This might be due to the rate of decomposition of calcium cyanamide in aqueous solutions of varying þH. The changes which cyanamide undergoes in acid and alkaline media have been described by Crowther & Richardson (1932). Solutions of commercial calcium cyanamide are moderately alkaline because of their lime content, and in this alkalinity any free cyanamide which is formed tends to polymerise to dicyanodiamide. Experiments with solutions of dicyanodiamide showed that this substance has very little toxic action on H. schachtii larvae. In acid solution, on the other hand, cyanamide is hydrolysed to urea. This substance becomes toxic when it decomposes to ammonia, but in the slightly acid solutions used the change would be a slow process. It is probable, therefore, that the degree of toxicity of calcium cyanamide solutions would be greatest where the cyanamide radicle could be retained unchanged for the longest period.

The problem of the vector of Onchoccrca gibsoni was investigated in Kuala Lumpur, F.M.S., where the parasite is endemic and a high percentage of cattle is infected.

For reasons which are outlined, the experimental work was confined to species of Culicoides and Lasiohelea of which 18, possibly more, species were found on cattle, some of them being found to bite cattle in very large numbers daily.

The distribution of the microfilariae of 0. gibsoni in the skin of live cattle was found to be very irregular, even within small areas of skin. In transverse sections of skin the microfilariae appear to have a maximum concentration just under the epidermis at a depth of ·05 to ·2 mm.

0·52% of 1,523 Culicoides pungens, which were dissected soon after an infective blood meal, were found to have picked up the microfilariae. 0·96% of 1,670 of this species, dissected some days after an infective blood meal, were found to have developing or mature filarial larvae in the thorax or head. 0·35% of 3,734 of this species, were found to be naturally infected with filarial larvae in the thorax or head. The difference between the experimental infection rate and the natural infection rate is shown statistically to be significant and it is concluded that C. pungens is an intermediate host of O. gibsoni.

Culicoides oxystoma, C. shortti and C. orientalis were also dissected in large numbers and were found to pick up the microfilariae of O. gibsoni; in each of these species the experimental infection rate exceeded the natural infection rate, but the difference in none of these is significant. It is concluded however, from the results obtained and from the morphological similarity of the mature larvae found in these species with that in C. pungens, that these species are also intermediate hosts of O. gibsoni.

C. peregrinus and C. buckleyi are suspected but not proven intermediate hosts. C. anophelis and/or C. anophelisv. flavcscens and Lasiohelea stimulans were found to pick up the microfilariae but only partial development was found in them. C. sumatrae and C. raripalpis also picked up the microfilariae but no development was found in them. The remaining species worked with were entirely negative. In view, however, of the very minute percentage of infection which occurs in Culicoides spp. and the large numbers which must be dissected to obtain positive results, the negative results given by these less common species are not necessarily conclusive.

1. In differentiating between species of snails various ratios of shell dimensions are frequently used as biological constants descriptive of the species. Some of the ratios commonly used are: length to breadth (L/B), length to length of body-whorl (L/W), length to length of shell aperture (L/l), and length of shell aperture to its breadth (1/b). Mean and extreme values of these ratios are given for small samples of five species of Limnaea.

2. In L. palustris the least variable of these simple ratios is L/W and the next best is L/l. Statistics are given for the distributions of these two ratios.

3. Data collected by Mozley are used to show that in L. palustris the ratio L/l (at least) is subject to considerable local variation, a fact which detracts from its value as a species constant.

One of the peculiarities of the eelworm Heterodera schachtii which makes it a very difficult parasite to control is the length of time it can survive in a dormant condition in the soil. In this state the embryonated eggs are protected by the resistant cyst wall, and, in the case of the potato strain of the eelworm, the larvae only hatch in large numbers in the presence of the host plant. On account of this property, land infected with the parasite remains infected even though the host plant is not grown. It is however well known that if “potato sick” land is rested from potatoes for a few years it is then sometimes possible to grow a potato crop giving a fairly good yield and showing little or no sign of sickness in the overground parts. In these cases, however, it is often found that the roots of the plants are heavily infested with eelworm. These and other observations have led to suggestions that other factors may be associated with H. schachtii in giving rise to the condition known as “potato-sickness.” Such factors may be due wholly or in part to soil conditions, climate, fungal attack or the time of attack by the eelworm. In some cases more than one factor may operate in addition to the nematode, and in different cases it is probable that different factors come into play.

During the microscopical examination of the debris collected by flotation from soil infected with the potato eelwormHeterodera schachtii Schmidt, the presence of small numbers of cysts unlike those typical of the potato strain has frequently been observed. The distinguishing characters of these cysts are their dark colour and their lemon-like shape. Similar cysts were seen by chance during observations on “clean” soil which was being used as a control to pot experiments with eelworm-infected soil. This “clean” soil had been obtained from a heap of top-spit material which had been removed from a field on Winches Farm known to have been under grass for at least twenty years, and probably longer.

1. The complacent attitude that fluke is no longer a disease of importance is attacked on the grounds that the recent low incidence of the disease is largely due to a temporary scarcity of the intermediary, Limnaea truncatnla.

2. A description is given of methods of making contacts, taking samples, and recording observations in a survey of typical habitats of L. truncatula in England and Wales.

3. Twenty-two such habitats are described in some detail.

4. These form the basis of a brief discussion on factors contributing to the ideal habitat, knowledge of which is desirable for the elaboration of new methods of control.

5. A provisional map showing the distribution of liver fluke in England and Wales is appended.

Fungi, which entrap and destroy small nematodes, have been known to mycologists for many years. Drcchsler, who, for a long time, has made a special study of these forms, has recently, in an important paper (1937), described and figured several species, including many new ones belonging to a number of different genera.

Amongst these fungi is one, Arthrobotrys oligospora Fresenius, which has long been known from the investigations of Zopf (1888) for its ability to capture, destroy and feed upon small free-living nematodes and also upon the larvae of Anguillulina tritici when supplied to it under experimental conditions.

There have been no previous records of nematode invasion of native grasses in Australia, although “Cockle” in wheat, caused by Anguillulina tritici, and root galls on wheat, due to A. radicicola are known to occur. Mr. J. E. Harrison, Senior Agrostologist, Department of Agriculture, Victoria, found Microlaena stipoides infected as herein described at Lorne in April, 1935. This seems to be the first record of the disease, but it has since been ascertained that it is widely distributed in Victoria.

The increasing mortality among domestic fowls in this country has of recent years drawn attention to the possibility that worms and other parasites may be factors in the causation of certain poultry diseases. Heavy infestations with worms are frequently observed on farms where mortality is high and although it is rare that death can be directly attributed to the parasites, it is thought that they might be responsible for loss of condition in the birds, and for lowering their resistance to disease. On the other hand, equally heavy infestations may be found in apparently healthy birds and the few experiments which have been carried out to test the pathogenicity of certain common intestinal worms have not shown any marked effect on the health of the birds as a result of the infestation. Further work along these lines is however, necessary before the pathogenicity of helminths in poultry and their relation to disease is understood.

The helminthic fauna of a number of Water Deer, Hydropoles inermis from Whipsnade Park has been examined.

Fourteen species of Nematodes were recovered, all of which were new records for this host.

Ostertagia lyrata and O. grühneri are recorded for the first time in England.

Trichostrongylus cervarius n. sp is described.

There appears to be a common belief among veterinarians that liver-fluke infections, caused by Fasciola hepatica, are only transient and that if the animals do not succumb to the disease the parasites pass out of the body in about nine months' time. For instance, Mönnig's “Veterinary Helminthology and Entomology” states on p. 39: “The flukes (Fasciola hepalica) usually live about 9 months in the sheep and then die and pass out through the intestine.” Clunies Ross & Gordon, in their “Parasites of Sheep in Australia” (1936), say: “The majority of flukes probably die after about 9 months but some at least may survive for 2 years.” One might question on what scientific evidence these statements are based. Thomas (1881), discussing longevity, says with regard to one sheep examined: “The ewe had been kept under conditions which render re-infection highly improbable, and it follows, therefore, that the life of the liver-fluke may extend beyond one year”

The differential blood count of the normal laboratory rat shows at all times a greater proportion of lymphocytes than of neutrophiles. In rats infected with 400–600 larvae there is within 2–4 days of the infection a great relative, and possibly absolute, neutrophilia with a corresponding lymphocytopenia, which becomes less marked as the infection progresses, though the percentage of neutrophiles remains above, and that of lymphocytes below, the normal average. This neutrophilia is accompanied by a moderate left shift in the Cooke polynuclear count which may persist for a considerable period. At the same time the infection is immediately followed by a relative eosinopenia or aneosinophilia which persists for 1–5 days and is probably due to the setting up of a local eosinophilia in the sub-mucosa of the intestine. Thereafter the eosinophilia becomes generalised and reaches its maximum in 7–16 days after infection, with considerable fluctuations from day to day, finally settling to a low-grade eosinophilia which may persist for some months. The degree of eosinophilia appears to be only generally related to the severity of the infection and depends on the individual host animal. Persistence of aneosinophilia is an unfavourable prognostic sign.

Preliminary investigations on the problem of affording protection to the potato plant growing in soil infested with cysts of Heterodera schachtii, were carried out by Hurst & Triffitt (1935, i, ii, 1937). In these experiments promising results were obtained by the application of calcium cyanamide or of ferric oxide to the soil, and trials with these chemicals were designed on a larger'scale. A small field experiment (Hurst & Franklin, 1937) was carried out in Lincolnshire during 1936, using dressings of 30 cwt. per acre of calcium cyanamide and 12 cwt. per acre of ferric oxide. On the cyanamide plots an increased yield of potatoes was accompanied by a relatively small increase in the cyst population of the soil. With ferric oxide the results were not significantly different from those on the untreated control plots.

Since 1935 a large number of chemicals including chloro-acetic acid and various water-soluble chloro-acetates, received from the Pest Control Committee of Imperial Chemical Industries, have been tested for their value in controlling the potato strain of Heterodera schachtii under the direction of Prof. R. T. Leiper, F.R.S.

Soils from Yorkshire and Ayrshire were used in the experiments, as they are of very different types, and might conceivably respond differently to chemical treatment.

The object of this short paper is to record a number of new host species for certain common helminths of birds. These new records show that the host range of some helminths is not so circumscribed as had been previously believed. Most of these parasites have been obtained at routine post-mortem examinations and hence were the result of natural infections in the field. A few however were the result of experimental feedings at this Institute.

Small galls on the leaves of Yarrow or Milfoil, Achillea Millefolium L., were first mentioned by Thomas (1873) but were investigated and described by Löw (1874) who made a new species of the causal organism under the name of Tylenchus millefolii. He dealt with the appearance, size and distribution of the galls, their presence on plants from spring to autumn and the ability of the parasite to revive from galls which had been kept dry from May to October. He described the general structure of the adult worms, gave particulars of their size and proportions, and, in addition to a sketch of a galled leaf, gave a drawing of the adult female and three views of the male tail.