Basilia hispida is the only insect parasite of the flat-headed bats Tylonycteris pachypus and T. robustula in Selangor, Malaysia where this study was conducted between September 1966 and August 1968. The climatic conditions in the laboratory closely approximated to those in the field: seasonal variations in climate were small but diurnal fluctuations occurred. The life cycle of the fly was not affected either by the season or by the sex or species of the host.

A typical life cycle was as follows: adult B. hispida reached sexual maturity within 5 or 6 days of their emergence from the puparium. Copulation largely occurred with newly emerged flies or with females at the time of prepupal deposition; one copulation sufficed for numerous subsequent offspring. The entire larval life of three instars was passed within the female, nourished by maternal secretions. After reaching maturity the female deposited prepupae at 9-day-intervals on the host's roosting quarters, deposition occurring during the day, stimulated by increasing temperature. The length of the pupal stadium depended upon the presence of a host bat; if one was present the pupal period was ca. 25 days. Thus the total life cycle from emergence of the female to the emergence of her first offspring was typically 39 (5 + 9 + 25) days. The sexes were produced in equal numbers. The greater part of postembryonic mortality occurred in the adult instar and was largely due to host-predation. Females were longer lived than males, and it was suggested that they had an average life expectancy of 5–6 weeks in the field.

The life cycle of five other species of Nycteribiidae from two other species of host were briefly examined and no major differences from B. hispida were noted. The results of this and of previous studies indicate that the life cycle is fairly uniform throughout the family.

1. Enzyme electrophoretic patterns from populations of snails, intermediate hosts of Schistosoma, have been examined.

2. Esterase patterns (α-naphthyl butyrate as substrate) have been used to differentiate snail populations of B. africanus and Biomph. pfeifferi.

3. Malate, β-hydroxybutyrate and α-glycerophosphate dehydrogenases may be of use in some cases to distinguish between species, e.g. B. africanus v. B. ugandae and Biomph. sudanica v. Biomph. pfeifferi.

The primary infection of breeding female rates with N. brasiliensis was examined as an experimental model for the study of the effect of lactation on host-parasite relationships.

Self-cure was inhibited when the period of infection corresponded with lactation, and a majority of worms could persist to day 34 when lactation was prolonged. A normal self-cure occurred during pregnancy, when litters were removed at birth or when the suckling litter was reduced to 3 young.

A detailed study of the structure of the tegument of D. phoxini has been carried out using probe and transmission electron microscope. The distribution of spines and sense organs on the forebody has been described, as well as the nature of the lappets in the everted and retracted state. The adhesive organ exhibits two different surfaces which also differ from the surface of the rest of the body. The use of the ‘Stereoscan’ has confirmed and extended the concept of surface specialization based on transmission studies.

A colony of the ixodid tick Hyalomma (Hyalommina) kumari was bred in the laboratory and all stages described. The known hosts and distribution of the tick in India are given briefly.

Acanthobothrium quadripartitum, a tapeworm parasitic in the intestine of Raja naevus, is not found in the closely related R. radiata. The tapeworm survives in vitro for over 24 h in fresh serum from the natural host, but fresh serum from R. radiata is extremely toxic; about 80% are killed within 2 h with the formation of a characteristic external precipitate. The toxicity of fresh R. radiata serum was abolished by procedures known to inactivate complement and restored by the addition of fresh serum from the natural host R. naevus. This observation suggests that both species of ray possess a similar complement system in fresh serum but only R. radiata contains a natural serum antibody toxic to A. quadripartitum. No toxicity could be demonstrated in R. radiata mucous in vitro, probably due to the serum factors being present in low concentrations.

The results are discussed in relation to the observed inability of A. quadripartitum to survive in the intestine of R. radiata.

Mouse blood infected with Plasmodium berghei berghei, P. vinckei vinckei or P. vinckei chabaudi, was injected intravenously into 10-day-old chick embryos, and 4 days later further mouse erythrocytes were injected; after 7 days the infection was passed to another embryo with more mouse erythrocytes, and so on. By this procedure, P. berghei was propagated for 39 days through 6 embryos, P. vinckei vinckei for over 45 days through 7 embryos, and P. vinckei chabaudi for over 67 days through 10 embryos. The plasmodia multiplied only in mouse erythrocytes; they invaded a few avian erythrocytes but did not proceed to schizogony in them. P. falciparum, P. knowlesi and P. cynomolgi did not survive in chick embryos longer than 2–3 days. Babesia rodhaini was maintained by this procedure for 9 days through 2 embryos.

The karyotypes of five species of Glossina are described.

Differences were found between karyotypes of different species, and also between different populations of the same species. These differences are discussed in relation to the phylogeny of the genus.

A new species of ascaridoid nematode, Baylisascaris tasmaniensis, is described from three marsupial carnivores of Tasmania, namely Sarcophilus harrisi, Dasyurus viverrinus, and Dasyurops maculatus. The new species is differentiated from other species in the genus Baylisascaris and the phylogenetic affinities within the genus are discussed in relation to the origin of the placental and marsupial carnivores.

Further investigations have been carried out on the nature of ‘host’ antigens associated with the adult worms of Schistosoma mansoni. These investigations show:

1. The ‘host’ antigens are not removed from the surface of the worms by thorough washing and prolonged incubation in Hanks's balanced salts solution. The antigens must be firmly bound or even incorporated at the surface.

2. Monkeys cannot be immunized against ‘mouse worms’ with mouse IgG immunoglobulins. Accordingly it is unlikely that the ‘host’ antigens are mouse anti-worm antibodies.

3. The ‘host’ antigens are certainly associated with the membranes of mouse erythrocytes. They may also be associated with the ‘soluble protein’ fraction of the erythrocytes.

4. Immunization with sheep erythrocytes failed to protect monkeys against challenge with ‘mouse’ worms. Therefore it is unlikely that the ‘host’ antigens are Forssman antigen.

5. The mouse ‘host’ antigens associated with ‘mouse’ worms are not major histocompatibility antigens. Consequently it is likely that they are species-specific mouse antigens.

Adult S. mansoni from a recently infected rhesus monkey (Macaca mulatta) were transferred into the hepatic portal systems of a normal rhesus and of a rhesus which had acquired complete resistance to the parasite. The worms were recovered after 2 days and examined by light and electron microscopy.

The worms recovered from the normal monkey were undamaged. Most of the worms recovered from the hyperimmune monkey were alive but had localized aggregations of host cells on their surfaces. Small areas of the tegument of these worms showed structural and degenerative changes, namely an increase in density and vacuolation of the tegument; the formation of small, round, membrane-bounded cytoplasmic bodies within vacuoles in the tegument; the breakdown of the outer membrane of the tegument and release of the cytoplasmic contents; and finally the complete disappearance of the tegument exposing the underlying muscle fibres. Host monocytes and polymorphonuclear leucocytes were closely applied to severely damaged parts of the tegument; the host cells appeared to be phagocytic. The other tissues of the worms were normal. Apparently the above damage is a result of the host's immune reaction which is directed against the tegument of the worms. Worms grown in mice and subsequently transferred to monkeys immunized against mouse antigens are similarly damaged, but in this case the damage occurs more rapidly.

Various endocrine operations were performed on the adult female cockroach Blatta orientalis and the adult populations of the nematode Hammerschmidtiella diesingi were recorded 2 or 4 weeks later. Cautery of the median neurosecretory cells (m.n.c.) caused a significant reduction in total numbers of adult nematodes after 2 or 4 weeks; after 2 weeks, removal of the retrocerebral complex (corpora cardiaca plus corpora allata) caused a significant overall reduction in the adult nematode burden and this could not be prevented by reimplanting the corpora allata immediately after the retrocerebral complex had been removed.

Anomalies appeared in the data when the sex of the parasite was examined and this may be related to a possible postembryonic mode of sex determination.

Both m.n.c. cautery and removal of the retrocerebral complex suppressed host terminal oocyte development and ootheca production, whilst reimplantation of corpora allata into ‘retrocerebralectomized’ cockroaches allowed reproductive processes to continue normally. Hence, the m.n.c. and corpora allata are essential for host egg development.

Histological studies showed a profound reduction in fuchsinophilic material in the corpora cardiaca of m.n.c. cauterized cockroaches.

Although the m.n.c. may affect the nematode directly or indirectly, a direct effect on the parasite by the corpora allata is unlikely.

An adult female Polymorphus minutus releases only mature eggs into the intestine of its final host. These eggs come from the pool of eggs in the body cavity of the worm which contains only about 30% of mature eggs, the rest being immature. An analysis of the age structures of the egg populations in the body cavity and the uterus shows that an assortment of mature and immature eggs has taken place as the eggs pass from the body cavity to the uterus. The uterus contains only mature eggs and these are the eggs which are about to be released. The only pathway whereby eggs can enter the uterus from the body cavity is through the uterine bell. This suggests that it is the uterine bell which is able to select mature eggs from the mixture of eggs in the body cavity.

A uterine bell in vitro engages in precisely patterned muscular activity which propels eggs through its branching lumen. In one part of the bell (the grooves between the median wall cells and the lappets of the uterine duct cells), the patterned muscular activity passes mature eggs into the uterus and immature eggs back into the body cavity to complete their development. The greater length of mature eggs seems to be the character which enables them to be ‘recognized‘ by the uterine bell.

The physical nature of the cercarial surface has been observed by several workers to change during the penetration of the cercaria through the skin and its metamorphosis into the schistosomulum. Very little is known about the chemistry of this change. This paper reports the effects of the treatment of the surfaces of cercariae and schistosomula with various reagents as assessed by light microscopy. It was found that there were great differences in the stability of the surfaces of these parasitic forms. The schistosomular surface was stable to 0·2 m acetic acid, 5% calcium chloride and 8 m urea, whereas the cercarial surface was affected by these reagents. 8 m urea completely dissolved the cercarial surface, while it had little visible effect on that of the schistosomulum. This dissolution of the cercarial surface could be prevented by including small quantities of sodium or calcium chloride in the 8 m urea solution. A method has been developed to isolate pure preparations of cercarial and schistosomular surfaces. Hypotheses about the chemical changes in the surface during metamorphosis should be amenable to investigation using this method.

1. A description of four new species of gregarine found in Blaberus discoidalis and Blaberus boliviensis is given. The species have been called Protomagalhaensia granulosae, Gregarina cubensis (from B. discoidalis), Protomagalhaensia blaberae and Gregarina princisi (from B. boliviensis).

2. A discussion of the taxonomic status of the species in relation to one another and to Gregarina blattarum and Protomagalhaensia serpentula is given, and further work to elucidate this problem is suggested.

The eggs of D. coeliaca have been cultured successfully and the free-swimming larva has been studied for the first time. The eggs have an incubation period which for monogeneans is exceptionally long (4–5 months at 10 °C). Apart from maintenance at a low temperature no other special conditions such as high hydrostatic pressure or washing to remove host body fluid are necessary for development. It is not necessary for the eggs to come into contact with host body fluid before development can begin.

The oncomiracidium of D. coeliaca has no eyes, a well-developed pair of anterior median gland cells and a pair of hamuli. The oncomiracidium of C. kroyeri is similar to that of D. coeliaca except for the presence of two pairs of conspicuous pigmented eyes, poorly developed anterior median gland cells, the presence of an extra pair of gland cells at the posterior end of the body and the absence of hamuli.

A comparison of the larval features of D. coeliaca and C. kroyeri has confirmed that these parasites belong to quite distinct species.

Gametocytes of a polychromophilid parasite indistinguishable from those of P. melanipherus are commonly found in the blood of the bent-winged bat Miniopterus schreibersii in New South Wales. There is a seasonal variation in infection rate, this being lowest in April (0%) and highest in August (up to 82·7%), and in density of parasitaemia.

This variation is the reverse to that found in the same species of bat in the northern hemisphere.

The reproductive biology of M. schreibersii in New South Wales is considered in relation to the seasonal variation in infection rate.

The main vectors of the parasitism are likely to be the nycteribiid flies, Penicillidia oceanica and Nycteribia parilis n.ssp.