The attempts of Chorine (1938), Gavrilov (1938), Gavrilov, Bobkoff & Laurencin (1938) and Rita (1940) to infect chick embryos with Plasmodium gallinaceum, using either a suspension of sporozoites or infected blood, yielded negative results. They tried inoculation by deposition of the infecting material on the chorion-allantois or by injection into a blood vessel of this membrane, and the negative results observed led Rita to make various deductions by comparing them with other infections which appear in the embryo and not in the adult animal.

For some years past in Northern Province, Nyasaland, work has been in progress to determine the mortality amongst native cattle due to east coast fever (Wilson, 1944). As an integral part of such a survey, routine tick collections were made during cattle inspections. It was then intended to map the various species of tick concerned in the hope that their geographical distribution might offer a partial explanation for the prevalence or absence of east coast fever in certain areas. Such a map for the western portion of Kenya Colony has been provided by Lewis (1939), ‘according to the groups of dominant species of ticks’; but in Kenya, climate, soils and vegetation show wide contrasting variations, and conditions are scarcely comparable to those existing in the smaller territory of Nyasaland.

A new virus disease of tomatoes is described for which the name tomato black-ring is suggested. The host range of the virus is wide but no insect vector has yet been identified. The longevity in vitro of the virus is 7 days or longer, the thermal inactivation point is about 58° C. and the concentration of the virus in the host plant is low. Tomato black-ring is essentially a disease of young plants which rapidly lose their symptoms if they survive the severe initial infection. The virus is carried without symptoms by a large number of miscellaneous plants.

Note added in proof. In a private communication Kassanis has pointed out that the tomato black ring virus produces enations on the undersides of the leaves of cucumber. The writer has confirmed this but finds that the enations develop only in the greenhouse type of cucumber, never on the outdoor or ridge variety. The enations do not seem to develop under winter conditions.

The writer's best thanks are due to Miss Margaret Short for her assistance in this work and to Dr Roy Markham for taking the photographs.

An account is given of experiments on the aphistransmission of the composite virus disease of tobacco known as rosette. It is shown that the component viruses—the vein-distorting and mottle viruses—persist for long periods in the body of the aphis, and that as many as twenty consecutive tobacco plants can be infected in 24 hr. serial transfers without the insect having recourse to a fresh source of virus.

The aphis Myzus persicae is the most efficient vector, the aphis M. convolvuli being less effective. The aphides M. circumflexus and Macrosiphum gei failed to transmit the virus.

It is shown that the mottle virus can only be transmitted by the aphis when it is accompanied in the plant by the other component of the rosette disease, the vein-distorting virus. The latter virus is easily transmitted by the aphis, either alone or in combination with the mottle virus.

The writer's best thanks are due to Miss Margaret Short for her assistance with the large numbers of aphis-transmissions, and to Dr Douglas Lea and Dr Roy Markham for suggestions in the course of the work.

The material which forms the basis of this note consists of two species of Anoplura, namely, Neohaematopinus echinatus (Neumann) and Hoplopleura maniculata (Neumann), both from the common North Indian five-striped squirrel, Funambulus pennanti pennanti Wroughton, collected at Benares (United Provinces). Since Neumann's (1910) description of the two species from ‘Sciurus palmarum Gm.’ (vide infra) from Rajkote (Kathiawar) and Scotophilus wroughtoni(?) from Navapur (W. Khandesh Dist.), there appears to be no other Indian record.

An account is given of the coprophilic habits of the holotrichous ciliate, Balantiophorus minutus Schew., and of the effect upon it of urine.

Experiments are described in which attempts were made to grow the ciliate in a wide range of human faeces of varying consistency and from both normal and diseased subjects. Abundant growth was obtained in normal faeces, both before and after dilution; but no growth took place in the undiluted faeces of softer or liquid consistency from various cases of intestinal disorder, even dilution frequently failing to render these a suitable medium. Moreover, the ciliate could not be recovered from such abnormal faeces by subculturing.

This behaviour was due to two primary factors:

(1) the high osmotic pressure obtaining in liquid stools which causes plasmolysis of the ciliates, and (2) the presence in the stools of unaltered bile salts, owing to the rapid passage of material through the intestinal tract. It was demonstrated that bile salts, even in very low concentrations, are highly toxic to B. minutus. Two secondary factors probably also serve to limit growth, namely, the presence of drugs with a toxic or depressing effect on the ciliate, and the presence of urine, which is not only highly lethal but also mixes more readily with a liquid than with a normal stool.

It was shown that the lethal action of urine upon the ciliate was due primarily to osmotic pressure, and, to a lesser degree, to the toxic effect of ammonia sometimes present in the urine. It was demonstrated that a concentration of urine as low as 5% inhibited multiplication in ordinary cultures, while as little as 1% prevented growth when admixed with normal faeces. It was further shown that urea has a depressing effect upon the reproduction of B. minutus. Paramecium caudatum was shown to be also susceptible to the lethal effect of urine.

Investigation of the effect of hypertonic solutions has shown that the limiting osmotic pressure which B. minutus can withstand for a prolonged period is represented by a solution of non-electrolyte with a depression of the freezing-point of about 0·60° C., or by a solution of an electrolyte with a depression of the freezing-point of 1·2° C. (represented by 1·9% sodium chloride solution) which is equivalent to about 6000 mm. Hg (8 atmospheres). It was also shown that osmotic pressure is not the principal limiting factor to the growth of the ciliates in such stools. The ability of other ciliates to live in hypertonic solutions is discussed and the conclusion is reached that B. minutus is more resistant than is usual among freshwater forms.

Experiments carried out on mice established that the cysts were incapable of passing through the mammalian alimentary tract and developing in the faeces after passage, so proving that B. minutus is an exogenous coprozoon.

It is concluded that (i) only polysaprobic Protozoa capable of movements in a viscous medium can lead an existence in undiluted faeces; (ii) under natural conditions urine probably acts as a limiting factor to the development of coprozoic ciliates in faeces; (iii) coprozoic Protozoa are derived from the soil fauna and have in turn largely contributed to the sewage fauna.

During the course of investigations into the distribution and seasonal activity of the tick, Ixodes ricinus L., in South Wales (Edwards & Arthur, 1945), a male tick was recovered which on examination was found to be a member of Ixodoidea, but which differed from the normal male of I. ricinus L. It was recovered from Margam Moors (Glamorgan, South Wales) by one of the writers (D.R.A.) in 1945, whilst dragging a blanket over rough vegetation, a method previously employed by MacLeod (1932) for the recovery of ticks from grassland. This is the only specimen of its kind which has been found, despite the examination of several thousands of males during the past three years. It has therefore been considered desirable to place on record a description of the form. When placed in a tube containing ten unfed females of I. ricinus, no mating occurred. Under similar conditions a typical male of this species mated with one unfed female within 7 minutes of its introduction.

1. The structure of the capitulum of I. ricinus L. is described briefly.

2. A stylet-like process is described in detail. Anteriorly it forms a distal attenuation, which widens out at its base near the point of attachment to the hypostome and is continued posteriorly as a distensible pouch overlying the pharynx. Anteriorly the stylet-like process is supported by a ventral sclerotized rod.

3. The stylet-like process effects closure of the pharyngeal orifice during contraction of the pharynx and so prevents the reflux of blood into the wound. In this it is assisted by the closure of the hypostomal gutter.

4. The stylet-like process appears to be a similar structure to that observed by Sen (1935) in three other species of Ixodid ticks and to be comparable in function to the tongue-like process described by Bertram (1939) in Ornithodorus spp.

The writer wishes to acknowledge his indebtedness to the Advisory Entomologist, Dr E. E. Edwards, in whose department the work was done; to Dr Alec Milne, Unit of Insect Physiology, Agricultural Research Council; Dr P. Tate, Molteno Institute of Parasitology, Cambridge, for reading the original script, for making many useful suggestions and modifications.

Several specimens of Phyllobothrium dohrnii (Oerley) were obtained from the intestine of Hexanchus griseus caught in the deep-sea fishing grounds on the Porcupine Bank to the west of Ireland. The species was first described by Oerley in 1885. Since then, several cestodes which are probably synonymous with this species, have been described by various writers. They are Crossobothrium laciniatum Linton (1889) from Odontaspis littoralis (the sand shark) at Wood's Hole, Mass., Crossobothrium campanulatum Klaptocz (1906) from Hexanchus griseus in the Gulf of Trieste, and Orygmatobothrium velamentum Yoshida (1917) from Cynias manazo (the bleeker) of Hiroshima, Japan.

Chloride regulation. Following the ingestion of a blood meal the tick excretes about half the ingested water in the coxal fluid. The mean haemolymph chloride concentration before feeding is 1.00% and after feeding 0.96% NaCl; and that of the coxal fluid, 0.80% NaCl. These results confirm the values given by Boné (1943).

Morphology of the coxal glands. These comprise the coxal glands proper, which elaborate the bulk of the coxal fluid, and the smaller accessory glands of unknown function. Each flask-shaped coxal gland consists of two distinct regions, an outer ‘filtration chamber’ and an inner system of tubules. The latter lead to the external opening. The filtration chamber, which communicates with the tubules at only one point, is highly folded into an elaborate series of pockets and fingers which closely invest the tubules; numerous small muscle fibres inserted in these pockets pass outwards from the gland to attachments on the body wall. The histology of the two regions is entirely different: the filtration membrane is only 1–2μ in thickness and its cellular origin is much obscured: the tubule walls are 5–30 μ in thickness, are composed of cells with a dense, deeply staining cytoplasm, and are richly supplied with tracheae. In Ornithodorus delanoei acinus the walls of the sac-like coxal glands are lined both by ‘filtration membrane’ and by large irregular groups of ‘secretory’ cells; there are no true tubules.

Function of the coxal glands. The production of coxal fluid is under muscular control. It is believed that the contraction of the coxal gland muscles enlarges the filtration chamber and sets up a sufficient pressure difference across the membrane to initiate filtration into the gland. In the subsequent passage of the fluid down the tubules threshold substances such as chloride are reabsorbed. That the coxal fluid is primarily an ultrafiltrate of the haemolymph is suggested by (a) the rapid passage of dyes and even haemoglobin into the coxal fluid after injection into the haemolymph and (b) the very high rate of liberation of fluid. Serum albumen sometimes passes into the coxal fluid after injection but casein (and the normal haemolymph proteins) are fully retained.

Arecoline hydrobromide was tested for its efficiency in causing dogs to purge and in removing hydatid worms by infecting, dosing and autopsying 157 dogs. Doses were given by mouth in water at various rates, by mouth in meat, and by subcutaneous injection.

The tabulated results indicate that the median efficiency of hydatid-worm removal, with doses of or above grain/10 lb. weight, are 95% or more. Dosing in meat is almost equally efficient but the action is slower, taking usually over 1 hr. instead of 15–30 min. Injections of arecoline caused purgation but not worm removal. Increasing the dosage rate above grain/10 lb. body weight increased the proportion of dogs that vomited and caused convulsions in some, but did not markedly increase efficiency in worm removal. The dose recommended for general use is grain/10 lb. body weight; though half or double this dose is about equally suitable. None of the dogs tested was killed by arecoline.

Repeated doses were given to see how many were required to ‘clear‘ a dog. Dogs usually gave negative results after three doses that caused purging.

Arecoline showed a similar high degree of efficiency against Taenia species and Dipylidium; usually removed about half the Toxocara specimens present, and had no significant effect against hookworms.

Solutions of arecoline were tested in vitro on isolated Taenia segments arranged to record. Solutions of 0.001% or more in Ringer's solution almost invariably caused extreme relaxation of the segment, its normal rhythmical contractions ceasing. The segments were not killed.

Arecoline hydrobromide appears to exert its anthelminthic action: first, by causing the muscles of cestodes to relax, so that the hold on the host's intestine is lost; secondly, by causing the host to purge, so that the detached worms are removed from the host's body.

The writer wishes to thank Sir Louis Barnett, Dr Hercus and other members of the Hydatid Committee for their interest and support. She especially thanks Miss D. Medley, Hydatid Assistant, who has carried out the heavy share of the infecting of dogs and handling of faeces. Thanks are also given to Mr L. K. Whitten, Agricultural Parasitologist, for technical advice; to Mr Grimmett, for analysing arecoline-content of pills; and to the various members of the Medical School staff who have given helpful advice.

A description is given of the processes of copulation, formation of the egg and spermatozoon, cleavage, embryogeny and hatching in B. phlebotomum. These processes were found to be essentially similar to those in other strongyle nematodes.

The anatomy of the first three larval stages is described and the observations of Conradi & Barnette (1908) and Schwartz (1924) were largely confirmed.

Penetration of the skin of calves by the infective larva was observed histologically. The larvae were found to have reached the dermis within 30 min. and to have penetrated the cutaneous blood vessels within 60 min. of application to the skin. The larvae were found in the lung where the third ecdysis was in progress 10 days after penetration of the skin. A description is given of the growth of the third-stage larva in the lung, the changes which take place during the third ecdysis, and the anatomy of the fourth-stage larva.

The fourth-stage larvae exsheath in the lungs and travel to the intestine. After a period of growth in which sexual differentiation takes place, the fourth ecdysis occurs and the adult parasite emerges. The time required for the attainment of maturity was found to be somewhere between 30 and 56 days after penetration of the skin.

This paper was written at the Ministry of Agriculture and Fisheries Veterinary Laboratories, Wey-bridge, and the writer would like to express his gratitude to the Director, Prof. T. Dalling, also to Dr W. R. Wooldridge, chairman of the Council of the Veterinary Educational Trust for their help and encouragement. The writer's thanks are also due to Dr H. A. Baylis, Prof. R. T. Leiper and Dr E. L. Taylor for their advice and help on technical points, and to Mr R. A. O. Shonekan, African laboratory assistant, for his able co-operation.

Investigations were carried out on the influence of the local environment on the preparasitic stages of B. phlebotomum and the following observations were made.

1. The infective larvae are positively thermo-tropic and positively phototropic. These observations confirm those of Schwartz (1924). The larvae are not negatively geotropic and do not climb grass, but remain in the dung, gaining access to the host by adherence of the dung to the skin.

2. Lack of air, such as would occur in tightly packed faeces; immersion of the faeces in water; temperatures below 10° C.; and lack of moisture, are all inhibitory to development. Infective larvae are resistant to at least 5 days‘ direct exposure to an atmosphere of relative humidity 75 at a temperature of 25° C.; in dry faeces they are resistant to 14 days‘ exposure to the same atmosphere.

3. In Northern Nigeria desiccation is the most important inhibitory factor in development. The extreme dryness of the pastures in the dry season prevents development of the larvae and adherence of dung to the skin. Penetration of the skin of the host probably occurs only in the rainy season, maximal penetration probably occurring just after the rains are regularly established.

4. The female lays 600 eggs in 12 hr. in the early rains, but the output of eggs by the females varies considerably throughout the year. It is greatest in the early rains and lowest in the later months of the dry season.

5. The female hookworm burden of nomadic cattle fluctuates throughout the year. The maximum burden occurs in the later months of the dry season.

6. Three factors, all probably bound up with a single factor, i.e. moisture, seem to influence the degree of pasture infectivity. (a) Inhibition of larval development; (b) failure of faeces to adhere to the skin; (c) fluctuation in the egg-laying rate of the female hookworms. The fluctuating pasture infectivity results in a fluctuating hookworm burden.

7. The period of maximum hookworm burden in nomadic cattle more or less coincides with the period of incidence of a disease in Stock Farm cattle, associated with hookworm infestation.

In the discussion an attempt is made to correlate these observations both in accounting for the seasonal incidence of ‘hookworm disease’ and in suggesting methods of control.

This paper was written during the tenure of a Cooper Centenary Fellowship for which the author is indebted to the Council of the Veterinary Educational Trust. The writer's thanks are also due to his laboratory assistant in Nigeria, Mr R. A. O. Shonekan.