The mites of the subfamily Trombiculinae are of special importance since, in the larval form, they are reported from many countries to be a nuisance to human beings by the intense irritation caused by their bites. At least two species of these larvae are the acknowledged vectors of scrub typhus (OXK typhus, ‘tsutsugamushi’ or Japanese river fever). The nymph and adult mites are free living and are known to be predatory, feeding upon the collembola and also on the eggs of ants, mosquitoes and collembola. In the larval stage they are found as parasites on mammals, birds, snakes, lizards and frogs. They have also been recorded upon a scorpion and upon three families of grasshoppers.

1. An account on the cercariae found in Melanopsis praemorsa common in the River Yarkon (Israel) is given.

2. A new species of Cercaria of the Pleurolophocerca group, Cercaria orospinosa, is described.

3. The development of C. orospinosa to the stage of metacercaria in the tadpole of Bufo viridis shows its affinity to the subfamily Cryptogoniminae (Hetero-phydae).

4. An artificial genus Velocercaria is proposed to comprise cercariae which have common morphology with Cercaria orospinosa and are characterized by the same type of tail-fins.

Trypanosoma cruzi has been examined with the electron microscope. Crithidia and metacyclic forms of a blood agar culture have been studied and compared with the adult tissue forms, obtained in tissue cultures, from the same strain.

In all the forms studied, the internal structure of the body is not revealed because it is too thick for electron penetration. In places where a good penetration has been obtained the cytoplasm shows a fine striation in spiral or parallel arrangement. This striation can be digested with trypsin or by prolonged osmic acid fixation.

Dense spherical bodies of variable size can also be observed in the body portion. They can be dissolved with xylene.

The whole body of the trypanosome is covered by a fine, transparent sheath.

The flagellum is formed by the axoneme which consists of five or nine fibres. It can be followed throughout the whole length of the metacyclic and of the adult tissue forms. In the crithidia forms of the blood-agar culture, it disappears in the anterior part of the body. The whole flagellum is covered by a fine sheath. The axial fibre bundle can be digested with trypsin or by prolonged osmic-acid fixation. Both, the striation and the fibre bundle are contractile structures which could explain the movements of the trypanosome.

Some dividing forms are also described.

A new species of Rhipicephalid tick, Rhipicephalus hurti, is described from game animals from the Rift Valley of Kenya. The new species is compared with R. capensis, R. serranoi and R. jeanneli.

My thanks are due to Dr G. Theiler, Onderstepoort, who confirmed that R. hurticould be correctly regarded as a new species and has been most generous in her assistance. My thanks are also due to Dr Santos Dias and Dr Hoogstraal for their most helpful criticisms; to Lieut.-Col. Hurt for his interest and care in sending me numerous tick-collections from the Naivasha area of Kenya; to Mr Alex Wiley and Mr Guggesburg for their careful drawings; and to Miss Walker, E.A.V.R.O., and my colleague Mr Pollard, for their generous help at all times.

This paper contains a discussion of the generic and specific characters of Tricho-nympha and Pseudotrichonympha, with a detailed account of the morphology of P. sertaneja n.sp. from a new species of Rugitermes.

The basic generic and specific characters of each organelle of Pseudotrichonympha are considered in detail. The genus Pseudotrichonympha has been separated from Trichonympha by the absence of the rostral articulation (citartrosi) and parabasal body. But in at least two species of Pseudotrichonympha a parabasal body has been found, and as Grassi himself believed that citartrosi, however feebly developed, must exist in all Pseudotrichonympha, the taxonomic position of Pseudotrichonympha needs further investigation.

The morphology of P. sertaneja n.sp. has the basic generic characters. The specific characters are discontinuous myonemes, oblique instead of longitudinal leiotropic striae, flagella of the first series covering not only the neck but the upper portion of the body, flagella of the second series confined to the basal part of the anterior triangular area of the body, flagella of the third series very short and of uniform size and simple outline of the ectoplasm.

The flagellate is regarded as a new species, named P. sertaneja n.sp. The host is a new species of Rugitermes from São Paulo, Brazil.

The whole life cycle of Paramphistomum microbothrium Fischoeder, 1901, found in cattle of Kenya, East Africa, has been established experimentally.

In laboratory conditions, the eggs hatched miracidia on the 14th to 16th day, if they were kept in water at a temperature of 26–28° C.

In a snail, Bulinus alluaudi (Dautzenberg), kept at the temperature of 18–20° C., the miracidium developed into a sporocyst, the elongated body of which, containing young rediae, reached a length of 3·6 mm. in about 2 weeks.

The first rediae which emerged from a sporocyst were observed on the 14th day, and on the 20th day the first generation rediae began to produce second-generation rediae. From the 28th day onward the first-generation parent rediae ceased to produce daughter rediae and began to develop cercariae only. This period of production of cercariae by the redia lasted about 30 days, and when the life of the first-generation rediae drew to its close, the old rediae developed a few daughter rediae again.

Cercariae began to emerge from the first-generation rediae 30 days after exposure of the snail to miracidia. The cercariae left the parent redia in a very immature state and further development occurred in the liver of the snail. The emergence of cercariae from the infected snail began on the 43rd day after exposure to miracidia. Shortly after emerging from the snail, the cercariae attached themselves to vegetation and encysted.

Development of rediae of the second, third, fourth and apparently more successive generations followed an identical course to that outlined for the rediae of the first generation. As a result the successive generations of rediae maintain the infection going in an intermediate host and the infected snails were continually shedding cercariae as long as they lived. In the laboratory experiments the life span of some of the infected snails exceeded a year.

In cattle infected experimentally P. microbothrium reached maturity and began passing out the eggs about a 100 days after the encysted cercariae were fed to the animals.

An illustrated account of a new species of Stephanonympha from the Brazilian termite, Neotermes hirtellus Silvestri, is given.

An historical introduction provides concise accounts of the previously described species of Stephanonympha.

The morphology of the new Stephanonympha is described in detail and illustrated.

Differential characters from previously described species of Stephanonympha are noted, the conclusion being that the Stephanonympha, of Neotermes hirtellus is a new species from a new host, to which the name Stephanonympha campinae n.sp. is given.

1. On the assumption that the limit of significant difference is 1%, it is necessary, when concentration methods are not used, to repeat the faecal examination 3 times for the egg of Ascaris lumbricoides, 7 times for hook worm and 11 times for Trichuris trichiura in order to obtain the diagnostic results obtained by the acid-ether concentration technique using 3 g. of faeces.

2. The coefficient of the identification by a single smear examination is 83·3% for eggs of Ascaris lumbricoides, 46·5% for hook-worm eggs and 33·6% for eggs of Trichuris trichiura.

1. A technique is described for the laboratory breeding of Musca domestica nebulo Fabr. the Indian house-fly.

2. Methods are described for the transferring of the flies from cages to appliances for testing insecticides and for close observation.

I am very thankful to Mr E. B. Raj-der-ker who kindly donated the B. K. Raj-der-ker insect breeding station for our work. I owe a debt of gratitude to the authorities of the Indian Law Society, Poona, who have placed land and building facilities at our disposal for this research. Prof. S. P. Agharkar placed all the facilities of the Research Institute of the Maharashtra Association for the Cultivation of Science at my disposal, and Mr D. R. Ranade voluntarily supervised the breeding at Poona.

An account is given of the general structure of Proteocephalus pollanicola. The genital system is dealt with in greater detail. The characteristic features of the species are enumerated.

The male portion of the reproductive system consists of 60–75 testes in a single layer; vasa efferentia with a lining epithelium; a wide, coiled vas deferens; a small cirrus-sac; a coiled ejaculatory duct and a short cirrus. A description is given of the histological structure of the male ducts.

The vagina opens anterior to the cirrus-sac. A well-developed vaginal sphincter is present. The seminal canal communicates with the oviduct and the uterine canal. An oocapt is present; the transverse vitelline ducts and the ovary open into it. A few unicellular glands are present hi the vicinity of the oocapt; these possibly represent Mehlis's gland. An ootype is absent. The histological structure of the female ducts is described.

The most conspicuous feature of the spiracle of Ornithodoros moubata is the so-called cribriform plate. This is a massive crescent-shaped vesicle consisting of three layers; the underlying sclerotized endocuticle, a series of branching pillars or pedicels arising from this basal layer and a very thin outer membrane, supported on the distal ends of the pillars and enclosing the whole structure (Fig. 1 A). The cavity lying between the basal cuticle and the outer membrane and ramifying between the pillars is continuous with the atrium of the spiracle.

Data concerning the life cycle of the various species of the genus Trichuris are somewhat controversial. The present paper is devoted to the study of T. muris, a common parasite of the caecum of wild house-mice and rats. The possibility of transfer of T. muris in the laboratory mice would enable the author to solve various contradictory points.

1. Methods of sampling pastures for infective larvae are discussed.

2. An account is given of the methods of operation and identification of larvae from herbage.

3. The distribution of larvae on pastures is discussed in relation to choice of method of sampling and interpretation of results.

4. The significance of grazing patterns to distribution of larvae is considered.

5. An attempt is made to evaluate the use and limitations of pasture sampling methods.

The author is indebted to the Agricultural Research Council for financial assistance in the form of a special research grant.

Contrary to results previously published, cortisone did not cause a rapid increase of parasitaemia in mice or hamsters infected with P. berghei, and in some cases it had an inhibitory effect. The existence of a humoral agent restricting the multiplication of the parasites in the peripheral blood was suggested.

In April 1953, several specimens of the common commercial mullet, Mugil cephalus L., heavily infested with cysts in the body cavity, were received. In May, June and July 1953, several specimens of the estuarine catfish, Netuma australis (Gunther) (Family Ariidae), similarly infected, came to hand. All specimens were taken from the lower reaches of the Brisbane River, Brisbane.

T. genypteri n.g., n.sp., is described from the stomach of the red ling, Genypterus blacodes Bloch & Schn., in coastal waters of Otago, New Zealand. This genus is characterized by having a small sucker anterior to the oral sucker and two muscle pads in the forebody.

The specimens described in this paper were collected in Assam by Dr M. L. Roonwal during World War II, and were sent to me for identification by Dr S. L. Hora, Director, Zoological Survey of India.

I am grateful to Prof. H. R. Mehra, Professor of Zoology, Allahabad University, for his able guidance, to Dr Hora for sending me the material and to Dr Charles D. Radford for his opinion on the species described in this paper.

In 1915 Glaser demonstrated for the first time that a nuclear polyhedrosis of a lepidopterous larva (Lymantria dispar), was induced by an invisible filterable virus isolated from the blood of diseased larvae. Nuclear polyhedroses of the larvae of over a 100 insect species are now known, and those of them which have been investigated have been shown to be due to viruses. In these polyhedroses the nuclei of susceptible cells, hypodermis, tracheae, fat and blood cells, etc., enlarge and become packed with infectious crystalline inclusion bodies, the polyhedra, from which the diseases get their name. The pupae and imagos of these insects are not generally susceptible to polyhedral virus diseases, and so far no nuclear polyhedrosis of imaginal tissues in the larvae has been reported. This has led to the suggestion that imaginal tissues are not susceptible to polyhedral virus diseases.

Experiments were designed to dissociate the effect of Eperyfhrozoon coccoides on the blood of mice from the effect of splenectomy. Both agents caused a decrease in number of red blood cells which was followed by an increased production of reticulocytes. The anaemic condition caused by the eperythrozoa persisted for more than 230 days after splenectomy, and parasites were seen in fluctuating numbers at intervals throughout this period.

At the height of infection, red blood cells were more fragile than normal in hypotonic saline and the blood clotted more rapidly than normal. No breakdown products of haemoglobin were detected in the urine or serum, and no haemolysins or haemagglutinins were detected in the serum. The white cell count was usually increased after heavy infections, the chief increase being in the number of myelocytes and other immature cells.

1. In intact rats infected with P. berghei spontaneous eradication of infection has occurred by about 4 months after the day of inoculation.

2. These recovered rats show a strong residual immunity to reinfection with a heterologous strain, but this has begun to wane by 15–18 months after cure of the initial infection.

I owe many thanks to Miss W. J. Wall and Miss J. Wrugh of the Ross Institute for maintenance of the rats and assistance with the blood films.