A technique for the hatching and subsequent in vitro cultivation of the oncospheres of Echinococcus granulosus, Taenia hydatigena, T. ovis, T. pisiformis and T. serialis to cystic larvae is described. The cytology and histology of developing larvae were also studied.

The basic culture medium consisted of medium 858 containing additional glucose and K+ supplemented with the appropriate host sera. Fresh sera from young animals was generally more successful in promoting growth than sera from commercial sources. Cultivation was carried out at 37°C in roller tubes with a gas phase of 10% O2+5% CO2 in N2.

The most successful results were obtained with T. pisiformis, oncospheres of which were grown to the cystic stage with development of hooks and suckers. During the later culture period, the bladder, although morphologically normal, ‘collapsed’ and did not retain its cystic shape.

In culture, larvae of T. pisiformis became motile at 3 days and at 5 days began secreting droplets from a glandular apical region; this region stained differentially in alcian blue.

Some larvae of T. pisiformis showed a tendency to undergo transverse or longitudinal fission, an effect possibly associated with the centrifugation applied during the early cultivation procedures.

Early cystic development was obtained with the other species studied, but experiments carried out were only of a preliminary nature. However, the development rate in these experiments approximated that recorded in vivo.

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.

Treatment of mice infected with S. mansoni by various sterilants effective against male rodents produced phases of inhibition of schistosome oviposition assessed by miracidial counts. In the treated worms, besides apparent disappearance of the testes, marked involution of ovarian tissue occurred. The gonads of both male and female worms seem to be directly affected by the antifertility substances. It is suggested that gamete production in both sexes follows similar lines in contrast to the finite reservoir of meiotic oocytes in mammals.

Eleven lepocreadiid trematodes from marine fishes of India are reported. Known species are: Aephnidiogenes senegalensis Dollfus & Capron, 1958, Lepocreadioides indicum Srivastava, 1941, Bianium plicitum (Linton, 1928) Stunkard, 1931, B. bombayensis Gupta, 1968, and Pseudocreadium patellare (Yamaguti, 1938) Manter, 1940. New genera are: Pseudolepocreadioides and Transversocreadium. New species are: Pseudolepocreadioides symmetrorchis, Transversocreadium cablei, Crassicutis karwarensis, Diplocreadium triacanthi, Lepidapedon longivesiculum and L. manteri. Bianium madrasi Gupta, 1968, is considered a synonym of B. plicitum and the genus Diplocreadium Park, 1939, is considered valid.

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 relationship between the ciliated epidermal cells and the subepidermal layer of the miracidium of Fasciola hepatica has been described. Non-ciliated ridge-like extensions of the subepidermal layer separate the ciliated epidermal cells from each other. The sunken portions of the subepidermal layer, each containing a nucleus, lie below the outer body wall muscles of the miracidium and open into the ridge by narrow neck-like connexions. Elongate vesicles, which may be a source of stored plasma membrane similar to that which occurs in the transitional epithelium of other animals, fill most of the ridge. In addition, characteristic round electron dense granules are found in the ridge but the majority are found in the sunken portions of the subepidermal layer.

The development and origins of the tegument of the sporocyst of F. hepatica have been described at the ultrastructural level. When the miracidium is in the process of penetrating the snail host, large vacuoles appear between the ciliated epidermal cells and the basal lamina which overlies the muscles of the body wall. These vacuoles have the effect of loosening the epidermal cells from the basal lamina of the body wall of the miracidium. Possible mechanisms involved in the formation of such vacuoles are suggested and discussed.

During penetration of the snail the ciliated epidermal cells of the miracidium are lost; the ridge, a syncytial layer between the epidermal cells which is connected with the subepidermal layer, spreads over the basal lamina and exposed body wall muscles of the metamorphosing sporocyst to form the new outer covering of the sporocyst.

Cytoplasm passes from the subtegumentary layer into the tegument during this stage of the development of the body wall of the sporocyst. Muscular contraction and microtubules may be involved in the outward movements of this cytoplasm. The nuclei of the subtegumentary layer remain below the muscles of the body wall.

Twenty-four hours after penetration of the snail the outer plasma membrane of the tegument forms folds, which greatly increase the surface area.

Sixty hours after penetration involutions between the folds, which may indicate pinocytosis, are present, and it is suggested that pinocytosis may play a role in food absorption.

The fully formed tegument is a syncytial layer containing numerous electron dense granules, vacuoles, mitochondria and lipid droplets.

The results on the formation of the tegument of the sporocyst have been discussed with reference to the controversy about the origins and terminology of the outer covering of the Platyhelminths.

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.

It has been shown that in common with other malarial species the drug response in the sporogonous cycle of Plasmodium cynomolgi parallels in a special way the drug response in the schizogonous cycle. Thus, prophylactic drugs produce deteriorating changes in the oocysts while curative drugs have a destructive effect on the sporozoites. A comparison of the effects of prophylactic drugs on the sporogonous and schizogonous cycles of the four malarial species studied thus far suggests the presence of more than one pre-erythrocytic developmental stage in the schizogonous cycles of P. vivax and P. cynomolgi following the initial invasion by the sporozoite.

Adult forms of the pig whipworm, T. suis, are able to establish intimate contact with the host's tissues by the formation of a tunnel-like construction which covers a section of the thread-like oesophageal region. The extreme anterior oral end and the stouter posterior region are not covered and lie free in the lumen of the caecum. The attachment tunnel is composed of host mucosal cells and goblet cell secretion and its possible mode of construction is discussed. Host tissue not directly involved in tunnel formation appears unharmed by the presence of the parasite. T. suis is therefore not a serious pathogen under natural conditions.

It has been demonstrated that characteristic structures of the trichuroid oesophageal region, e.g. bacillary band and stichosome are metabolically active. The former penetrates the layered cuticle in the form of columnar protrusions originating in the hypodermis. Each hypodermal column represents a gland cell or bacifiary cell, which displays enzymic activity, e.g. acid phosphatase, non-specific esterase, glucose-6-phosphatase, succinate dehydrogenase, cytochrome oxidase and β-d-glucosidase. Its possible function at the host-parasite interface and in the metabolism of the whipworm is discussed. The layered cuticle is proteinaceous and enzymically inert.

Glandular activity is also displayed by the stichosome surrounding the capillary-like oesophagus. This evidence confirms earlier suggestions that the stichosome is a series of oesophageal glands.

Although the bacillary band may be involved in nutrient uptake the evidence obtained indicates that this is via the mouth which is favourably placed for the ingestion of mucoid material which was detected in the oesophagus. This may be subjected to preliminary hydrolysis by the enzymes present in the oesophagus and stichosome.

Eggs of T. colubriformis and H. contortus were separated from faeces. Their response to desiccation was compared by subjecting them, at different stages of development, to a range of relative humidities. Many eggs of T. colubriformis at all stages of development survived desiccation at relative humidities down to 75%, whereas the only H. contortus eggs to survive were those exposed to the highest relative humidity and which had already undergone a substantial amount of development before desiccation.

1. Both male and female N. fasciatus normally require a blood meal before they will mate.

2. Fed males do not attempt to mate with unfed females. It is suggested that the taking of a blood meal enables the female to provide a stimulus necessary for the male to show mating behaviour.

3. Unfed Nosopsyllus of both sexes will mate if subjected to a temperature between 30 and 35°C inclusive. Above 35° mating does not occur.

4. Below 30°C mating occurs only if the fleas have previously been subjected to a temperature of 30°C or above. A temperature rise to the critical point thus acts as a trigger for an enabling process which continues after temperature has again fallen.

5. It is suggested that the effect of a blood meal in enabling mating to occur may be explained by the fleas' experience, while on the host, of a rise in temperature to the level critical for mating.

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.

It has been shown that in samples of the eggs of T. colubriformis, the smaller eggs (i) have a greater probability of survival when incubated at fixed temperature and saturation deficit; (ii) require less time to develop and hatch when incubated in water at constant temperature, and (iii) have a greater surface area relative to volume, than do the larger eggs.

A hypothetical basis for the relation between egg size and desiccation survival is briefly discussed.

Growth and development of S. venezuelensis in percutaneously infected albino rats was studied and compared with S. ratti. The development of S. venezuelensis was found to last longer than that of S. ratti, the difference resulting mainly from the longer sojourn of the L3 larvae in skin and lungs. The growth rate was found to differ in each developmental stage, being higher in L4 than in L3 larvae. The adult females continued to increase in size for 6–7 days postexposure. The increase in body width, oesophagus length and tail length was found to be allometric bradyauxetic.

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.

1. The distribution of filarial larvae in the dorsoventral and dorsal-longitudinal muscle fibre groups was studied in serial sections of mosquitoes of a susceptible strain of Aedes aegypti infected with Brugia pahangi or subperiodic B. malayi and of wild-caught Mansonia uniformis mosquitoes containing the latter parasite.

2. The experiments showed that more larvae were situated in the dorsal-longitudinal muscle than in the dorsoventral and that the difference in numbers was highly significant.

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.

The distribution of S. ratti and S. venezuelensis in the intestine of albino rats was studied in experiments with single species infections and in mixed infections.

The majority of S. ratti were found in the anterior 20 cm of the intestine and in decreasing numbers in the remaining 60 cm. The larvae of S. ratti settled in the Lieberkühn crypts where they matured and laid eggs in convoluted tubes.

The parasitic females of S. venezuelensis were concentrated in the anterior 15 cm of the intestine, with over 50 % in the anterior 5 cm, and a few worms 20–25 cm posterior to the pylorus. The larvae settled in the villi, close to the surface of the mucosa. The straight egg strands were laid on this site.

It was concluded that, although occurring together, the two species can coexist in the intestine without interfering with each other.

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.

Both fed and unfed rabbit fleas can move relatively slowly upwind towards a host. The speed of movement is too slow for direct host location from more than a few cm.

Fleas are strongly attracted to a urine bait, will remain gathered around it, and can move rapidly on to a host when one is present.

The attraction is produced by physiologically realistic amounts of urine, little increase being obtained from volumes greater than 15 ml, even over a tenfold range. The range of movement of fleas towards a urine bait obtained in our experiments was greater than 6 m but less than 9 m. The maximum survival time in pasture during summer and autumn was between 14 and 21 days.

The attractants are contained in urine and not in faeces, and are not restricted to the urine of rabbits or even of lagomorphs. Strong attraction was obtained towards hare and rat urines, and a low degree of attraction towards dog and human urine. Concentrated homogenates of rabbit anal glands gave low attraction.