1. The functional anatomy of the ducts associated with Mehlis's gland in the echinostome Artyfechinostomum mehrai (Faruqui) recovered from a girl has been described.

2. The mechanism and histochemistry of egg-shell formation are described and discussed.

Appreciation is extended to Dr V. S. Raghunathan, M.D., Physician and Superintendent, and Dr T. Sreenivasan, M.D., of King George Hospital, Visakhapatnam, for their kind co-operation and the gift of specimens of A. mehrai. My thanks are due to Professor P. N. Ganapati for facilities and encouragement.

The development of Amplicaecum robertsi has been followed from the egg to the adult stage using laboratory mice and rats as intermediate hosts. The eggs were found to be resistant to desiccation and would develop under water; they were infective to mice after culturing for 18 days after removal from the uterus.

Completion of the first moult occurred after hatching of the eggs in the intestine. Within 6 hr. of infection second-stage larvae had reached the liver. They also appeared in the lungs and carcass, but after 2 days were mostly confined to the liver.

At 5–7 days after infection larvae underwent a period of lethargy followed by the second moult and the third-stage larvae commenced a period of growth reaching a length of 79 mm. at 28 weeks after infection in the liver of mice. In rats the growth of the larvae was slower for the first 2 months, but eventually they reached more or less the same proportions as in mice. The intestinal caecum appeared at a length of 3–4 mm., but there was no development of the reproductive organs throughout the third stage and no evidence of the third moult in rodents.

Fifty carpet snakes were autopsied and searched for larvae and adults of A. robertsi; in two snakes third-stage larvae were found in the aorta; in one snake the third moult was observed in the wall of the stomach and oesophagus; in three snakes the fourth moult was observed in the wall of the stomach; in twenty-six snakes adults were found.

Experimental infection of laboratory-reared carpet snakes showed that infection with embryonated eggs resulted in second-stage larvae in the tissues which did not develop further. Infection with third-stage larvae, resulted in two distinct migratory patterns depending upon the maturity of the larvae administered. Larvae from the liver of laboratory rats which had been infected less than 12 weeks previously, migrated to various tissues, especially the aorta, of the snake, where they remained coiled in cysts filled with clotted blood for periods up to 112 days. Growth occurred within these cysts, but no evidence of moulting was observed. In contrast, larvae from the liver of laboratory rats infected 12 weeks or more previously, and from mice infected for 8 weeks or more, underwent the third moult in the wall of the oesophagus and stomach of the snake.

With the onset of the fourth stage, the development of the reproductive organs became evident and continued during the fourth stage. It appeared that the fourth stage may occur in two phases, possibly depending on the size of the third-stage larva at the time of ingestion. Some experimental infections indicated that third-stage larvae may give rise to attached fourth stage larvae, probably capable of active growth. Other observations indicated that fourth-stage larvae may remain encapsulated in the wall of the stomach or oesophagus until sex differentiation is completed, after which the fourth moult occurs and the adult parasite emerges, leaving two sheaths of the same length within the capsule.

The functional significance of each of the larval stages is discussed and it was concluded:—that the first-stage larva is one of tissue differentiation, whereby development proceeds to the infective stage; that the second stage represents a migratory phase without structural changes; that the third stage represents a growth phase, characterized by considerable increase in size, but without further radical changes in differentiation.

In contrast, the fourth stage is characterized by absence of growth, inability to migrate, and by marked structural changes in the reproductive organs, whereby the sexes are differentiated. Evidently this development may take place while the fourth stage is attached to the wall of the stomach or oesophagus, or while the larva remains in the capsule in a state of quiescence.

The fourth moult may occur in the attached state, but usually occurs within the capsule. After it is completed, the adult may remain for an indefinite period within the capsule with the two sheaths of the third and fourth stage. The emergence of the adult worms may be influenced by the arrival of food in the stomach. Once this phase is initiated, both growth and reproductive activity ensue during the adult stage.

This work was financed by a research grant from the University of Queensland. The writer wishes to acknowledge the valuable assistance of Miss Ann Pritchard.

The paper records the description of the morphology and taxonomy of a new genus and species of a Heterotrichous ciliate (family Clevelandellidae) found in the gut of the non-xylophagous termite Capritermes incola Wasm. (Termitidae) from Dharwar (India).

Notocotylus is reported in Indian domestic fowl and the specimen assigned to the species N. attenuatus. The literature on this monostome genus is briefly reviewed and need for an examination of type specimens of some of its species is stressed.

Thanks are due to the Principal of the college for facilities provided and to the head of the Zoology Department, Lucknow University, for loan of some literature.

The morphology of the adult blood fluke Schistosoma hippopotami sp.nov. from Hippopotamus amphibius L. is described and compared with that of other species of the genus Schistosoma.

Common (1952, 1954) found a mermithid that parasitized the bogong moth, Agrotis infusa (Boisd.) during its resting period on the walls of caves in Australia. Nematode material that he collected was given to Dr J. B. Goodey, Rothamsted Experimental Station, Harpenden, Herts, England, who found it to contain two species. This material subsequently was given to me, and on examination each species was found to be undescribed. A description of each follows with a suggested life cycle and some remarks on the unusual parasitism of adult insects by the mermithids. This material permitted a re-examination of the taxonomy of the genus Amphimermis Kaburaki & Imamura, 1932.

A study of the changes in the worm burden in calves receiving daily doses of infective larvae of Ostertagia ostertagi indicates that the following processes occur:

(1) A constant loss of adult worms at a rate depending on the number present.

(2) An inhibition of development in the early fourth stage which depends partly on the presence of adult worms. This inhibition is not irreversible; larvae resume their development, the number which do so depending on the number present.

(3)A stunting of adult worms, those developing late in the infection failing to grow as large as those which developed earlier.

(4)An inhibition of ovulation, distinct from the stunting, which prevents worms developing later from becoming as prolific as those which developed earlier.

(5)A resistance to the establishment of newly acquired worms, which begins to operate after prolonged exposure to infection.

The loss of adult worms and their replacement by the further development of fourth stage larvae leads to a frequent exchange of populations of adult worms.

The effect of these phenomena in determining the course of the infection is discussed.

Whilst examining amphibian helminths collected from Pahang, Malaya, a hitherto undescribed species of Oswaldocruzia was found among them. In a previous paper (Yuen, 1962), I have recorded the only other Malayan species of Oswaldocruzia: namely O. hoepplii Hsu from Bufo melanostictus Boulenger, Rana macrodon Boulenger, and R. cancrivora Gravenhorst from various parts of Singapore.

This paper records two new species of Amplicaecum from Malayan amphibians for which the following names are proposed: Amplicaecum communis sp.nov. and A. sandoshami sp.nov. A. communis is a common parasite in a number of Malayan amphibians, but A. sandoshami has been found only in Megophrys sp.

This work contains the description of two new Coccidia parasitic in the South American lizard Cnemidophorus lemniscatus lemniscatus. One is identified as Eimeria flaviviridis americana subsp.nov., which is described and discussed in relation to the other species recorded from sauria. The other is Hoarella garnhami gen.nov., sp.nov., whose position in the family Eimeriidae necessitated a revision of the classification of the Coccidia Eimeriidae.

I wish to acknowledge the help and encouragement I received from Professor P. C. C. Garnham, in whose department this work was carried out. My thanks are also due to Dr Cecil Hoare for his private communications and assistance in the interpretation of histological specimens. The author is grateful for co-operation of the School's Photograph Staff and to members of the staff of the Department of Parasitology, especially to Mr P. E. Nesbitt for his valuable sections. Finally, the author is indebted to the Consejo de Desarrollo Cientifico y Humanístico de la Universidad Central, Caracas, for their assistance in the form of a scholarship during the tenure of which this work was produced.

An attempt has been made to study the movements and feeding habits of juvenile forms of Fasciola hepatica as they pass through the wall of the host's intestines during the first 24 hr. of experimental infections in the mouse. Metacercarial cysts were fed to mice in large numbers (100–500) and the flukes were examined by means of sections during excystment and as free flukes and flukes making their way through various tissues. Excystment is regarded as essentially a feeding operation, the young fluke breaking through the fibrous inner cyst by the physical action of the ventral sucker in weakening the wall and the oral sucker in the actual breakthrough. Free forms were found in sections of infected intestines both in the lumen and lying between the villi, and penetrating forms were located inside the villi, in the submucosa and passing through the muscular layers and the serosa. A great deal of evidence was accumulated which indicates that the young fluke is able to break down epithelia, connective tissue and unstriped muscle fibrils and to feed upon the resultant products, thus proving itself to be a tissue feeder in the broadest sense of the term. The fluke's passage through the intestinal wall is by a devious route, tangential to the mucosa for some distance and then usually diagonally through the muscular layers, following the direction in which the circular muscle cells are oriented but cutting across the longitudinal muscle cells. This is probably due to the angle which the rim of the oral sucker makes with the longitudinal axis of the body, and it is a modification of the browsing habit which is seen when the feeding fluke lies on a plane surface. The tissue feeding proclivities of young flukes were also displayed in instances of penetration into lymph nodes and adipose tissue. These evidences support the opinion previously expressed by the writer that flukes migrating through the hepatic parenchyma, which are merely forms a little older and larger than the forms studied in the present researches, cannot be regarded as blood-feeders in the strict sense of the term but must also be regarded as tissue feeders. Attention is directed to the fact that very few digenetic trematodes have caecal outgrowths and that Fasciola and Fascioloides stand apart from all other genera in having dendritic outgrowths of the intestines. It is remarked also that the development of the ramifications of the intestines in Fasciola hepatica occurs during the first month, and largely during the second week, of juvenile life when the young flukes are eating their way through the hepatic parenchyma. During a few days the ramifications of the caeca develop to a greater extent than occurs during the entire lifespan of all other digenetic trematodes, with the exception of Fascioloides magna.

Histological investigations of the bile ducts of various hosts of F. hepatica during the early stages of infection, when the flukes are burrowing in the liver and have not yet reached the bile ducts, indicate that subtle changes are brought about, probably by chemical agencies and as a result of the inflammatory process, in the bile ducts of the hosts. The transitory appearance of minute cytoplasmic blebs at the free margins of the epithelial cells seems to inaugurate an intense hyperplasia of the epithelium with tubular ingrowths and adenomatous development of glandular tissue, and an associated fibrosis which produces a thick underlying layer of dense fibrous tissue. At the time of entry of the flukes into the biliary system the hyperplastic epithelium is intact, but soon the spines and suckers of the flukes abrade the superficial cells until this part of the duct is completely denuded. It is suggested that as a result of the inflammatory reaction, the fluke has been provided with a ‘pasture’ of hyperplastic epithelium and connective tissue on which it may continue to browse for considerable periods without necessarily affecting the host adversely. Tissue debris is found in the contents of the bile duct and similar homogenized materials occur in the caecal contents of the fluke. Previous researches have shown that the fluke will feed on various tissues, and it is suggested that this tissue-feeding habit persists during its life in the bile duct. These results agree with the findings of Müller (1923) but are at variance with the results obtained by other investigators, as is shown in discussion. The hyperplasia of the bile duct is not characteristic of fascioliasis, occurring also in clonorchiasis, opisthorchiasis and dicrocoeliasis, and in these and possibly other instances it is probably intimately connected with the nutrition of the flukes concerned.

During the early stages of infections of mice with Fasciola hepatica (6–11 days) the young flukes feed almost exclusively on hepatic cells which the oral sucker and the pharynx have broken down into a kind of homogenate containing Kupffer cells, invading leucocytes and some erythrocytes. As the flukes increase in size liver damage also increases in amount because of the larger burrows which are made. In some instances this does not adversely affect the host but in many infections excessive liver damage produces critical conditions which threaten the life of the host and its parasites. A comparison of the lesions produced in infections lasting 17–25 days with lesions produced after only 6–7 days has shown that the former, unlike the latter, are not due entirely to the feeding activities of the fluke. In short-term infections the inflammatory reaction produces the characteristic effects which are concerned with the healing of fluke tracts, but in older infections this reaction appears to be much more violent and tremendous leucocytic infiltrations break down apparently normal hepatic parenchyma and convert the terminal part of the burrow into a pool containing enormous numbers of invading leucocytes, broken hepatic cells and blood. These are the conditions which prevail at the onset of the critical period, when flukes have their growth inhibited as if by nutritional deficiencies. Some hosts are able to survive the critical period and nurture well-grown flukes for long periods, and may be able to obviate the critical conditions. It is suggested that the excessive damage which occurs in many instances during the critical period is not due to the feeding activities of the larger flukes but is a consequence of less restrained or even unrestrained inflammatory reactions which may lead to more serious pathogenic effects bordering on malignancy. This may be related to differences in the time spent by flukes in the hepatic parenchyma, early entry into the biliary system obviating these effects, late entry facilitating them.

1. In all species of the fusca group of tsetse flies (Glossina), except G. brevipalpis Newstead, a gelatinous structure, the genital fossa, is present at the anterior end of the uterus. On the surface of the genital fossa is a toughened structure known as the signum.

2. Probably chitin and certainly calcium are present in the substance of the signum of G. tabaniformis Westwood. An opaque concretion develops on the signum after the female has been fertilized. The concretions may be caused by a reaction between sperms or secretions from the male accessory glands and materials in the substance of the genital fossa; the possibility that the concretions are ‘mating scars’ produced by pressure of the harpes of the male on the signum is considered unlikely. Concretions are not present on the signa of all species.

3. A possible mechanism of fertilization in G. tabaniformis is discussed, and it is suggested that the signum may act as a protective shield for the anterior part of the uterus and common oviduct of the female from the harpes of the male which are inserted into the uterus during coitus. The views of Machado (1959) are discussed and it is agreed that the signum probably acts as a protective shield in all species in which it occurs and differences in the form of the signum between species may be related to differences in the form of the harpes of the male.

I wish to thank Dr J. Williamson for chromatography, Dr L. E. Stephen and Mr K. E. Broomfield for advice and assistance with the sectioning of the signa, Dr F. Peers for operating the Flame Photometer, Dr D. G. Godfrey for suggesting that the signa should be examined for calcium, and Mr W. Petana for taking the photomicrographs.

I am indebted to Dr K. C. Willett, Director of the West African Institute for Trypanosomiasis Research, for criticism of the manuscript.

Satchell (1947) described and keyed the larvae of 14 of the 19 British species of Psychoda, but this study did not include P. humeralis Mg., presumably because the author accorded generic rank to Philosepedon and Threticus which would put them outside his study of Psychoda sensu stricto. The larva of P. humeralis has been briefly described by Spärck (1920), but his figures are rather crude. A detailed treatment of the larval head is given by Anthon (1943). The present account is offered to facilitate identification of this species in the larval stage when used in conjunction with Satchell's comprehensive paper.

The observations presented in this study indicate that the filose projections emerging from the apical or luminal surface of the epithelial cells lining the caeca of the trematodes Cleptodiscus kyphosi and C. reticulatus are sterocilia or microvilli. Their activity in the animal appears to be concerned with the absorption of substances from the lumen of the blindly ending caeca rather than with movement of material.

Acknowledgement is made that part of this work was carried out in the Department of Zoology and Anatomy of the University of Nebraska, Lincoln, Nebraska, and supported in part by a grant from the Nebraska Heart Association for 1959.

When Acridine Orange was dispersed in cod-liver oil, its characteristic green fluorescence remained unaltered following absorption of this mixture into the peripheral circulation from the intestine. This result implies that there was little or no change in the lipid or its suspensoid as a result of undergoing this physiological process. The selective combination of this dye in aqueous solution with the cytoplasmic components of specimens of Trypanosoma lewisi, also present in the blood smears with the droplets of the green-appearing oil, resulted in an alteration of fluorescence as indicated by the rose red appearance of these organisms.

The present findings on the absorption of lipid droplets, containing a fluorochrome, by trypanosomes occurring simultaneously in the circulation of rats confirm similar observations reported by Wotton & Halsey (1957). The possibility is suggested again that fats and oils may serve as pharmacological vehicles for orally administered trypanosomides for the elimination of trypanosomes.

Part of this study was carried out in the department of Zoology and Anatomy of the University of Nebraska, Lincoln, Nebraska, and was supported in part by a grant from the Nebraska Heart Association for 1959. We would like also to extend our appreciation to the Division of Laboratories of the Nebraska State Health Department of Lincoln, Nebraska, for the use of their ‘Fluorex’, ultraviolet illumination microscope unit.

In a survey on the worm parasites of cats in Calcutta, Chandler (1925) mentioned the common occurrence in dogs also of Echinochasmus perfoliatus (Ratz, 1908) which has also been listed by Bhalerao (1935) in cat, dog and man. According to Verma (1935), the dogs at Calcutta harboured three distinct flukes—a species of Echinochasmus, a heterophyid and a third species described by him under a new genus, Episthochasmus, as E. caninum. In a survey of the helminth parasites of pariah dogs examined at Calcutta, Mapleston & Bhaduri (1940) included Echinochasmus sp. amongst the six new records from India. Chatterji (1954) regarded Episthochasmus as a synonym of Episthmium Lühe, 1909 and Stephanoprora Odhner, 1911, Echinochasmus and Episthmium Lühe, 1909 as subgenera of Echinochasmus. A new species, based on two specimens collected from the intestine of pariah dog at Allahabad, was described as E. (Echinochasmus) canai. Relying on the character of the forward extension of vitelline follicles, Stephanoprora was to include forms with vitellaria extending to the posterior margins of anterior testis, Echinochasmus forms with vitelline follicles extending beyond the anterior testis but not anterior to the anterior margin of ventral sucker and Episthmium forms with follicles extending beyond the anterior margin of this sucker. Thus, Verma's species was named as E. (Episthmium) caninum.

The new species of Amblyomma described in this paper was collected and forwarded to the author for identification by Mr J. H. Calaby, Wildlife Section, C.S.I.R.O. This is the fourth species of the genus to be recorded from Western Australia, the others being A. australiense Neumann, A. albolimbatum Neumann, and A. triguttatum Koch (Roberts, 1953).

A n.gen. and n.sp. of a yeast-like micro-organism—Adlerocystis ornithodori—is described. This micro-organism is probably a symbiote of sperm cells of Ornithodoros tholozani. Another species, A. parkeri n.sp., is found in O. parkeri.

Adlerocystis sp. were also found in O. coriaceus, O. nicollei, O. erraticus, and O. savignyi.

The earliest stage of development of A. ornithodori was observed in the posterior lobe of the complex of accessory genital glands of the male, where it has the shape of a round cell. It is spindle-shaped when attached to the mature sperm in the spermatophore.

The development of A. ornithodori from a round cell to an elongated spindle-shaped organism, in vitro in the spermatophore, as well as in vitro, is described.

We wish to thank Dr W. Burgdorfer, the Rocky Mountain Laboratory, Mr R. Garcia, University of California, and Mr A. Avivi, the Israeli Institute of Biology, who provided ticks, as well as Mr E. B. Kennedy for taking the microphotographs and Mr N. Shultan from the Elyahu and Rosa Wunsch Electron Microscopy Laboratory for the electron micrograph, both from the Hebrew University Hadassah Medical School, Jerusalem.