Whilst studying the development of Fasciola hepatica, I observed that the “collar” of the redia was rarely so prominent as it was figured and described by Thomas (1883). This observation, and a consideration of the mechanical requirements of the case, led me to suggest (1927) that Thomas was incorrect when he attributed to this structure the function of maintaining the circular section of the redia.

Early in 1925 I received from Mr E. Jacobson a mite taken in 1918 from the Passalid beetle Gnaphalocnemis (Eriocnemis) burmeisteri Kaup. on the east coast of Sumatra. It clearly belonged to the genus Megisthanus, and was apparently new. I had described and figured it before I showed it to Mr Stanley Hirst of the British Museum (Natural History), South Kensington. He informed me that he had received both sexes of what he believed to be the same mite, and most kindly offered to hand over to me the material to complete my account of the new species. By the courtesy of Sir Sidney Harmer he was permitted to do this, and I have therefore been able to examine, as regards external features, four female and three male specimens.

Dans le pus des ulcérations du gros intestin on trouve toujours en nombre plus ou moins considérable des macrophages d' un type spécial. On tencontre ces macrophages dans la dysenterie bacillaire, dans la dysenterie amibienne, dans le colitis ulverosa (cette dernière a, pour moi, une origine non infectieuse).

My interest having been aroused in Calliobdella lophii, I requested all my friends engaged upon the sea to keep a look-out for any leeches that might come to hand and especially for Calliobdella. Accordingly on 6. VIII. 1914 I received a specimen of a leech, taken near St Margaret's Hope towards the north-east of S. Ronaldsay in the Isles of Orkney, which as far as I can discover has never been described before, and which presents peculiar and interesting features not wholly dissimilar from those of Calliobdella. I propose to name the leech Ganymedes (or, if this name should be pre-occupied, Ganymedebdella) cratere.

Mr C., who has lived for ten years in the tropics, was under the care of Dr de Jong and myself for chronic amoebic dysentery. Some five years ago he suffered from an abscess of the liver, readily cured after operation. Before this abscess he had never noticed any dysenteric symptoms, but afterwards he often had mild, or sometimes more severe, attacks of recurring dysentery, most times without fever. During the attacks, the bloody slime contained a great number of amoebae, principally of Entamoeba histolytica and containing erythrocytes. With an “emetine cure” the attacks regularly subsided; but between two attacks the patient produced constantly a great quantity of so-called “minuta forms” and 4-nucleate (“tetragena”) cysts of this species in the faeculent parts of the stools. After an emetine treatment I often found a rather sudden increase in the number of cysts (always measuring from 11·5–13·5μ), sometimes to a tremendous amount. Several times we tried to get rid of the amoebae by a cure with emetine bismuthous iodide, but without success, so the patient stayed under observation and regularly sent us his stools for control.

During an investigation extending over several years of the forms of Trypanosoma lewisi, as met with in naturally infected Mus decumanus, I have met with many phases which I have not seen described.

The publication of this list of Reptilian Trematode parasites involves little comment. Reptiles form at most an insignificant and unobtrusive part of the fauna of this country and, apparently, few if any, investigations have ever been made of the Trematode parasites which may occur in them. I have personally examined a few snakes but with entirely negative results.

The object of the enquiry reported on below was to determine, if possible, the method of infection of Lucilia caesar, L. with Herpetomonas luciliae, a common parasite of the alimentary tract of the fly, the subject being not too remote from the kalaazar problem to lack interest.

In the Upper Mississippi River Region, invasive faucet snails (Bithynia tentaculata) and their trematode parasites have been implicated in more than 182 000 waterfowl deaths since 1996. Estimating transmission potential depends on accurate assessments of susceptible host population size. However, little is known about the mechanisms underlying snail–host susceptibility in this system. Prior field studies suggest that very small, likely young, faucet snails are less suitable secondary intermediate hosts. Here, we test whether the patterns observed in the field are because small snails (1) are refractory to infection by cercariae, (2) die from infection and are removed from sampled populations, and/or (3) are not preferred by cercariae. Our own field collections were consistent with the observation that smaller faucet snails exhibit lower metacercarial infection prevalence and abundance than larger snails. However, laboratory-based experiments show that smaller snails were actually more susceptible to infection than larger snails. Moreover, the smallest snail size class had significantly higher mortality than larger snails following infection, which may explain their reduced infection levels observed in the field. Our study demonstrates the importance of pairing field and laboratory studies to better understand mechanisms underlying patterns of infection.

Cutaneous leishmaniasis (CL) is one of the most disregarded tropical neglected disease with the occurrence of self-limiting ulcers and triggering mucosal damage and stigmatizing scars, leading to huge public health problems and social negative impacts. Pentavalent antimonials are the first-line drug for CL treatment for over 70 years and present several drawbacks in terms of safety and efficacy. Thus, there is an urgent need to search for non-invasive, non-toxic and potent drug candidates for CL. In this sense, we have implemented a shape-based virtual screening approach and identified a set of 32 hit compounds. In vitro phenotypic screenings were conducted using these hit compounds to check their potential leishmanicidal effect towards Leishmania amazonensis (L. amazonensis). Two (Cp1 and Cp2) out of the 32 compounds revealed promising antiparasitic activities, exhibiting considerable potency against intracellular amastigotes present in peritoneal macrophages (IC50 values of 9.35 and 7.25 μm, respectively). Also, a sterile cidality profile was reached at 20 μm after 48 h of incubation, besides a reasonable selectivity (≈8), quite similarly to pentamidine, a diamidine still in use clinically for leishmaniasis. Cp1 with an oxazolo[4,5-b]pyridine scaffold and Cp2 with benzimidazole scaffold could be developed by lead optimization studies to enhance their leishmanicidal potency.

Temporal changes in glucose transport capacity in excysted scoleces of Hymenolepis diminuta were examined. Assays involved incubation for 1 min in [3H]glucose after pre-incubation for 1 min to 8 h in saline. There were two abrupt increases in uptake velocity, a relatively small one between 15 and 75 min, and a large one between 5 and 6 h, during which the Vmax increased from 0·36 to 2·49 nmol/25 larvae/h. The second increase was unaffected when the pre-incubation saline contained 5 mM glucose, but it was completely blocked when the excysted larvae were pre-incubated in Ca2+-free saline. Abrupt glucose transport changes did not occur in intact cysticercoids or in scoleces when the substrate was [3H]leucine or [3H]uracil. Arrhenius plots (log V versus 1/temperature, 10–42 °C) were linear for intact cysticercoids, but were biphasic for both scoleces and adults with discontinuities at 20 ± 1 °C. Thus, ‘activation’ of the excysted scolex seemed to involve a specific, Ca2+ -dependent increase in number of glucose transporters functioning in the worm surface. The Arrhenius plots indicated that development in the final host does not involve a major change in lipid composition of the parasite's membranes.

A standard culture technique is described for obtaining the various developmental stages of Trichostrongylus colubriformis, and a suitable technique for assessing the effect of methyl bromide fumigations is outlined.

Doses of 10, 25 and 150 mg. hr./l. were required to give an LD50 for eggs, pre-infective and infective larvae respectively. The age of infective larvae, the relative humidity and the temperature all influenced the toxicity of the fumigant. Soil, and more especially faeces, sorb the fumigant and probably protect larvae from its full effect. Infective larvae of T. axei, T. retortaeformis and H. contortus were also found to be susceptible to methyl bromide.

The activity of larvae surviving fumigation was considerably reduced, but these larvae were still capable of infecting guinea pigs.

Methyl bromide killed common pasture grasses at doses of 150–250 or more mg. hr./l., depending on the temperature. Chloropicrin was found to be highly toxic to grass and unsuitable where the pasture is required undamaged.

The results are discussed in the light of current theories of the mode of action of methyl bromide on insects and what is known at present of the physiology of nematodes.

It is concluded that under certain conditions, methyl bromide might be used to eliminate infestations of trichostrongyle larvae on pasture, without killing the pasture.

I am indebted to Professor B. G. Peters and other members of the staff of the Imperial College Field Station and Dr C. W. R. Spedding of the Grassland Research Institute, Hurley, for their help in this work and their advice and criticism.

Patients infected with Schistosoma mansoni showed an abnormal response to a test dose of tryptophan, with little increase in the urinary excretion of kynurenine, hydroxykynurenine, xanthurenic and kynurenic acids, N1-methyl nicotinamide, methyl pyridone carboxamide, 5-hydroxytryptamine or 5-hydroxyindoleacetic acid. In contrast to previous reports, this is different from the pattern of tryptophan metabolism seen in vitamin B6 deficiency. Furthermore, the patients' plasma concentrations of pyridoxal phosphate were within the reference range, and supplementation for 5 days with 20 mg vitamin B6/day did not affect tryptophan metabolism. Treatment with a single dose of Praziquantel resulted in a substantial restoration of normal tryptophan metabolism. In mice infected with S. mansoni there was a similar impairment of tryptophan metabolism, as shown by considerably reduced formation of 14CO2 after the administration of a tracer dose of [14C]tryptophan. Again, the administration of vitamin B6 supplements did not correct tryptophan metabolism in the mice. Treatment with Praziquantel resulted in substantial restoration of the production of 14CO2 from [14C]tryptophan. There was no evidence of vitamin B6 deficiency (as determined by erythrocyte aspartate aminotransferase activation coefficient) associated with infection in the mice, although there was a redistribution of pyridoxal phosphate between tissues, with a reduction in the concentration of liver, spleen and kidney, and an increase in skeletal muscle.

On examination of a house mouse (Mus musculus) trapped in Rifa village (Assiut Governorate), a Trypanosoma cruzi-like trypanosome was encountered which differed from the cruzi-like trypanosomes of local bats. It appeared to be a hitherto unknown species for which the name Trypanosoma (Schizotrypanum) assiutis sp.nov. is suggested.

The nervous system of the female of Thelastoma bulhõesi is described. Three granular lobed structures, presumably arcade cells, are present at the anterior end of the female and of the male.

The only mode of transmission of Nyctotherus ovalis from one cockroach to another was shown experimentally to be by way of ingestion of the encysted stage of the ciliate. The cysts were remarkably resistant, being able to remain viable for 21 weeks at −18°C. if kept in dry faeces, or for 20 weeks in wet faeces at 4°–25°C. Their life was much shorter if kept at 37°, 25°, or 4°C. under dry conditions, or at −18°C. under wet. The cysts could withstand freeze-drying, or storage in pure oxygen, carbon dioxide or nitrogen, at least for short periods.

Nyctotherus ovalis could excyst in any of the four species of cockroach which were tested (Periplaneta americana, Blatta orientalis, Blattella germanica, Blaberus giganteus), irrespective of the species of origin. The ciliate could establish an infection in a very young host; in a host which had ingested infected faeces once only; in hosts which were in a very dry or a very humid environment; in a host maintained at a temperature far below that required for in vitro excystation, subject only to the temperature being high enough for it to be possible for the cockroach to digest its meal; but Nyctotherus could not establish an infection in cockroaches which were about to moult, because there was no movement nor digestion of food in the gut. There was no evidence of an instinctive drive on the part of the cockroach to eat infected faeces. There was some evidence that the Blatta and Blattella types of trophozoite and cyst were associated with the presence or absence respectively of a type of flora typically associated with the hind-gut of Blatta.

The process of excystation took as little as 3 hr. for completion in vivo, but this time was increased if faecal material was ingested along with cysts. The process was most rapid in the smallest cockroach (Blattella) and slowest in the largest (Blaberus). The process, once started, could be completed in vitro, but at a considerably slower pace. Digestion of the knob on the cyst by the cockroach's enzymes seemed to be necessary if the ciliate was to emerge.

A small proportion of cysts hatched after passage through the gut of a locust, but no means were found of increasing this proportion, and an infection was never established. Excystation did not occur in any other arthropod, nor in the frog, which were tested.

Cysts recovered from the mid-gut of a cockroach completed the process of excystation in vivo more rapidly if they were put in a buffer medium of pH approximating that of the mid-gut than if they were put in saline. Passage of the cysts through the foregut of the cockroach had no function in stimulating excystation: the agent seemed to be the trypsin secreted by the mid-gut caeca, or the products of its activity. The many failures in the series of experiments which are reported here can probably be attributed to contaminating bacteria.

The complete process of excystation could occur in vitro if the cysts were incubated with faecal matter from the cockroach. The optimum temperature was 32°C., and 2 days were needed for a significant number to hatch. No means were found of shortening this time, nor any agents which could be substituted for the faecal matter. The stimulus seemed to be provided by particular anaerobic bacteria of the faeces which were present in some cockroaches, but absent in others.

Work by other authors on excystation in other Protozoa is reviewed. It was concluded that in vivo excystation of Nyctotherus ovalis occurs as a result of stimulation of the cyst by the digestive trypsin of the cockroach, and not by the products of the unidentified bacterium which is active in vitro. Cysts originating from Blaberus seemed to be less sensitive to this bacterial factor than some of those from Periplaneta or Blatta.

This work was done during the tenure of a Research Studentship awarded by by the Agricultural Research Council. I am deeply indebted to Dr P. Tate for his encouragement and counsel at all stages of the work.