The species of the genus Ancylostoma (Dubini, 1848) reported as parasites of the human intestine are A. duodenale, A. braziliense, and occasionally A. caninum and A. malayanum. “Creeping eruption ” is considered to be a cutaneous helminthiasis produced by larvae of an ancylostome that American authors accepted as A. braziliense. As a result of detailed studies of the parasite by Lane (1922), Darling (1924) and Schwartz (1927), the majority of parasitologists now treat A. ceylanicum as a synonym of A. braziliense, contrary to the opinions of de Faria (1914,1916) who described A. braziliense, and Looss (1914) who described A. ceylanicum. The solution of the problem is not only of systematic but also of epidemiological importance because de Faria (1914) expressed the opinion that A. braziliense is not pathogenic for man. In the present enquiry the writer has been able to demonstrate that A. braziliense and A. ceylanicum are two different species; and for this reason it is considered of interest to summarise the original descriptions of the two nematodes and the existing opinions concerning this problem.

1. Observations were made on the development and hatching of eggs of Aspiculuris tetraptera in different media, preparatory to experiments investigating the possible occurrence of retrofection in this Oxyurid. Eggs of Enterobius vermicularis were studied under similar conditions.

2. Infective eggs of A. tetraptera were applied to the anal opening of clean mice which were immobilized in cages specially designed to prevent the possibility of oral infection. Of 12 mice treated thus evidence was obtained from 6, by the finding of immature or adult worms in the intestine, that retrofection had taken place. This constitutes the first experimental proof of the occurrence of retrofection in a non-human Oxyurid.

Tests were conducted using a capillary microbalance to estimate the errors introduced as a result of weighing out replicate cyst batches in place of counting.

Experiments with differently sized samples showed that the normal relationship between sample size and accuracy applied to such cases, the error for samples of 100 cysts being usually of the order of less than 10%. There is some evidence that the errors in cyst number introduced as a result of weighing is reflected by an increased error in the larval count, although under the conditions of experiment the increase was barely significant. It is suggested that if replication is increased by 50% or 100% then errors due to inequality in cyst numbers are more than counteracted.

In 1911 Looss wrote as follows : “ Up to the present time Agchylostoma duodenale is known to occur with certainty only in Man. It is true that the older works and text-books state that it has also been found in various species of animals (some species of apes, the tiger, the dog, the horse, etc.). In opposition to these statements, attempts made on various occasions to infect adult dogs, cats, rabbits, guineapigs, rats, mice, etc., with the parasite yielded entirely negative results. Only with quite young dogs and cats (not more than three or four months old) was the infection partly successful. The results of all these attempts at artificial infection thus support the view that the older statements as to the natural occurrence of Agchylostoma duodenale in animals are founded on a confusion of this species with others …”

Four samples of D-D were tested at six dosage levels for their nematicidal activity against the potato-root eelworm Heterodera rostochiensis; the treatments were carried out on naturally infested soil in 5-in. pots, viability being estimated by hatching in root diffusate. There was no evidence of there being significant differences between the samples at 50–60% kills, but at higher and lower kills they did appear to differ appreciably from one another in nematicidal activity.

1. A new Dicrocoelid trematode, Leipertrema rewelli n.g., n.sp., from the pancreas of an Orang Utan which died in the London Zoological Gardens, is described, and the relationships to other genera are discussed.

2. A male and female Dirofilaria from the peritoneal cavity of the Orang Utan are described and identified as D. immitis (Leidy, 1856).

3. Reasons are advanced for the view that D. pongoi Vogel and Vogelsang, 1980, is a synonym of D. immitis.

The original McMaster slide (Gordon and Whitlock, 1939) has been extensively used for investigations involving dilution counts on helminth ova in faeces. In view of the simplicity inherent in its design and use, attempts have been made to utilize it for obtaining estimates of the viable egg contents of cysts of Heierodera rostochiensis, the use of a modified McMaster slide for this purpose being described by Fenwick (1942). Fenwick's slide differed from the original in that the counting area was marked on the floor of the counting chamber instead of its roof; this modification resulted from the use of water as a diluent instead of semi-saturated brine as used in faecal examinations. The capacity of the original McMaster slide (0·15 ml.) was, however, found to be too small to give a reasonably large count from a batch of 100 cysts unless the degree of dilution was so small that efficient agitation before the withdrawal of a sample for counting was difficult.

During March, 1950, the writers visited a 15-acre field of mixed oats and vetches near Lechlade, Gloucestershire, because it was reported that the crop was patchy and that both oats and vetches were diseased. Inspection of the field revealed typical “tulip-root” symptoms in the oats, while many of the vetches were severely dwarfed and showed browning of the lower parts of the stems. Subsequent examination of plants in the laboratory showed the presence of large numbers of Ditylenchus dipsaci in the oats and a rather lighter infestation in the vetches; in the latter the eelworms seemed to be associated particularly with the necrotic tissues in the lower parts of the stems. It may also be mentioned that young docks, probably Rumex crispus L., from the same field were found to contain D.dipsaci.

The finding of tares or common vetch, Vida sativa L., attacked by the stem eelworm, Ditylenchus dipsaci (Kiihn) Filipjev, reported in the foregoing paper by Staniland and Southcy and the correspondence on the subject which passed between Staniland and Goodey, brought to light an interesting point in regard to the accuracy of the first record of the parasite on this particular host which calls for some comment and elucidation.

1. The investigation shows that the spring increase in worm egg output of Scottish hill sheep is correlated with an increase in worm burden.

2. The increase is mainly due to members of the Trichostrongylidae, and of these the stomach worms, Ostertagia spp. and Trichostrongylus axei, are the most important.

8. This increase in the worm burden in the spring is due to larvae picked up at that time, and there was no evidence that any were lying dormant throughout the winter in the mucous membrane of the abomasum and small intestine.

1. An experiment in bush-clearing was carried out at a small endemic focus of onchocerciasis in South Kavirondo district with a view to observing its effect on the adult population of S. neavei.

2. The clearing consisted of the complete removal of undergrowth and partial removal of trees, from the banks of fly-infested portions of two confluent rivers, the Riana and the Yabe.

3. In the first year of the experiment the clearing was carried out on the infested section of the Riana River, after which there was a decrease in the incidence of S. neavei on this section compared with that on the uncleared Yabe River.

4. In the second year a similar clearing was effected on the infested section of the Yabe River, after which the S. neavei incidence on both sections came together again and during the third year showed a steady increase.

During the detailed study of the finer anatomical structure of the potato tuber nematode, Ditylenchus destructor Thome, 1945, the presence of an apparently hitherto unrecorded structure was revealed. It is situated on the ventral surface of the body just anterior to the excretory pore. It is quite easily seen in living nematodes and has no doubt, in the past, been confused with the excretory pore. It appears as a bright lens-like structure, more highly refractive than the neighbouring parts, especially when specimens are viewed in an approximately lateral position. The structure is really band-like, usually more or less biconvex in section, situated between the cuticle and hypodermal layer.

An account is given of further observations on the distribution of the beet eelworm (Heterodera schachtii Schm.) in the period 1944–1950. Scattered infections occur in eastern England from South Yorkshire to the Thames and outlying infections suggest that the eelworm may be more generally dispersed. As yet, there are no records of beet eelworm occurring in Scotland. The limitations of the method of field survey are briefly discussed.

The foregoing results throw light on the conditions under which hatching tests can be carried out. In the first place, pre-soaking cysts in water for a period of 10 days increases the rate of larval emergence but has no effect on the total number of hatchable larvae. Increase in temperature has a similar effect up to 25°C, but at 80°C. hatching is virtually inhibited. Volume of diffusate per cyst is without effect either on the number of hatchable larvae or on their rate of hatching. Neither was any effect observed from alterations in pH between 8.2 and 8.1. The effect of dilution is more or less linear when dilution is plotted geometrically against cither the number of hatchable larvae or the latter expressed as a proportion of the original cyst contents and subjected to angular transformation. For the effect to be appreciable, dilution must be of a high order. Dilution to a half or a quarter of the original concentration has little appreciable effect. The effect of dilution on the rate of hatching is not obvious and the variations in it resulting from dilution are probably random. Direct sunlight inhibits hatching, diffused daylight is without effect as compared with darkness ; cysts exposed to the action of sunlight and diffusate do not hatch when later removed to the dark. It appears reasonable to assume that this may be due to some lethal effect.

Immersion of cysts of Heterodera rostochiensis in potato-root diffusate results in larval emergence which may occupy up to two or three months. In a previous paper (Fenwick, 1950), the author dealt with the form of the hatching curve, and showed that any given curve was controlled by three parameters; the number of larvae finally emerging, the mean reaction time of the hatchable larvae and the standard deviation of that mean reaction time expressed in log-time units. Since it was also shown that each of these parameters was subject to considerable variation, it is obvious that maximum information and accuracy can only be obtained by continuing a hatching test until all larval emergence has ceased and plotting cumulative hatches at selected intervals of tune against log-time; in this way detailed information may be obtained regarding the parameters of the hatching curve.

In their preliminary paper (Fenwick and Franklin, 1942) on the identification of the cyst-forming species of the nematode Heterodera by means of the length of the larvae, the present authors studied methods of preparing the larvae for measurement and of making the measurements, and considered the form of sample to be taken from a population of Heterodera larvae which would give the most reliable estimate of the mean length of the whole population. Those studies were made on the larvae of H. rostochiensis only, but the ultimate purpose was to obtain strictly comparable estimates of the mean lengths of the larvae of all the known species of Heterodera in order to find out whether larvae of the different species could be identified by their length.

1. Observations on Fasciola hepatica in Limnaea truncatula under laboratory conditions showed that the cercariae did not emerge at temperatures below 9°C. Above 9°C. emergence proceeded indiscriminately up to the limit of experimental observation (26°C).

2. Experience showed that emergence occurred in the light or in darkness while changes in the hydrogen-ion concentration of the water containing the snails (within the range 5.5 to 8.5) had no effect on emergence. There was some evidence that an increase of carbondioxide in the water slowed but did not inhibit emergence but depletion of oxygen had no apparent effect.

3. In the laboratory, emergence could be induced by removing snails from dry habitats and immersing them in water or by removing snails from watery habitats and placing them in fresh water. We were unable to determine the exact physical.or chemical factors acting as a stimulus under such conditions.