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.

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.

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.

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.

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.

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.

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.

Merocysts in P. inornatus are found in the liver, spleen and lungs, while in P. magnificus the liver is the only site. In the former the protoplasmic rim is narrow and the merozoites are sparsely distributed within it; in the latter the protoplasmic rim is irregular, quite thick and broken in places. In the former, the colloidal mass is scanty, and is in the form of tenuous matrix enclosing irregular interspaces; in the latter form, the colloidal mass is in the form of homogeneous substance with little vacuolation. In view of the wide differences in the structure and the site of occurrence, the merocysts found in the two different species of flying squirrels are considered to belong to two separate parasites. The parasite occurring in P. inornatus is identified as H. rayi rayi Tokura & Wu, sensu stricto, while the other parasite occurring in P. magnificus is designated H. rayi wui, a new subspecies, named in honour of Dr Wu Chen-Lan who worked on flying squirrel malaria in Formosa.

Heavy infections of E. acervulina result in a depression in body weight of the host, but anorexia induced by the disease is not the only factor responsible for this, since normal birds starved to the same extent did not lose as much weight. It was shown that the absorption of l-histidine and glucose from the infected part of the small intestine was depressed and may be a contributory factor to this weight loss; restricted feed intake alone tended to increase, rather than decrease, absorption.

Suppression of P. berghei infections but not those of N. rodhaini or T. brucei in mice on milk diet were noted. The suppression of P. berghei was variable. This was not due to differences of the quality of the milk or to the mice eating faeces, sawdust, etc. which may be rich in PABA. The variability was at least partially due to selection of a strain of parasite probably requiring a lower level of PABA than normal. One such strain was isolated and its pattern of infection compared with the normal strain. The ‘milk diet’ strain caused a higher fatality rate in mice on milk diet but always showed a lower parasitaemia growth rate in mice on normal diet. When repassaged through mice on normal diet, the ‘milk diet’ strain did not revert immediately to the infection pattern of the normal strain.

The course of the worm burdens of calves infected daily with larvae of Ostertagia ostertagi at five different rates was studied by making post-mortem worm counts on groups of calves killed after experiencing infection for different periods of time.

The relationship between worm numbers and infection rates together with evidence that a turnover of worms occurred, led to the conclusion that burdens of adult worms were regulated primarily by a loss of worms at a rate proportional to the number present.

Further, estimates based on the number of developing fourth-stage larvae indicated that the proportion of the larvae administered which became established decreased gradually as the experiment progressed.

At very low infection rates, the rate of turnover of the worms was slower than at high infection rates but in all groups it remained constant through the 6 months duration of the experiment.

The development of a small proportion of the larvae administered was arrested at the early fourth stage. At the highest infection rate used, the proportion of worms that became inhibited was somewhat greater.

The distribution of N. brasiliensis within the small intestine of rats, following a primary infection, is described.

The fourth stage larvae were found to inhabit the sections later parasitized by the adult population.

Both the larval and adult worms were found to be confined to the anterior half of the small intestine. This aggregation is believed to be under the influence of stimuli (factor(s) 1), present in the lumen of the host gut.

The adult worms also clumped within the already confined worm population. This behaviour is thought to be due to intrinsic behaviour patterns of the worm, sexual attraction and thigmokinesis.

Larval and adult worms were surgically transferred to points, at varying distance from the ‘normally’ inhabited region, in the small intestine of fresh recipient rats. The resulting migratory behaviour of the worms was studied.

The worm populations resulting from both the larval and the adult transfers showed the ability to recognize that they were in the wrong position of the small intestine and to be able to orientate, migrate and locate the ‘normal’ site.

Owl monkeys infected with the Malayan Camp strain of Plasmodium falciparum were found to have malarial antigens in their serum at the height of infection. The antigens were identical with certain malarial S-antigens present in the sera of West African (Gambian) children acutely infected with P. falciparum. The infected owl monkey thus appears to provide an experimental model which is relevant to the study of the serology of human malaria.

The capillariid nematodes present in passeriform hosts collected in Taiwan are recorded and described. Two new species are established, Capillaria parusi sp.n. from Parus monticolus insperatus and Sitta europaea formosana, and C. madseni sp.n. from Corvus macrorhynchus colonorum, and their affinities are discussed. Capillaria tridens, C. longifila and C. contorta are recorded from a number of new hosts.

A hypothesis to explain some features of Ascaris flexures is given. It is based on the co-operation of muscle cells in domains which may assume two states. In one state the muscles are long and it is mainly the non-contractile parallel elements that are in tension. The other state has short muscles exerting tension mainly in the contractile elements. The living animal changes shape if new domains are formed or if domain boundaries move. The hypothesis is applied to laboratory experiments and observations.

Few workers have studied the amino acid requirement of larval Digenea in vivo. Cheng (1963) conducted a study of three species of parasites, each from a different host, and suggested that both free and bound host amino acids act as food sources. His assumptions are based on the disappearance of free amino acids from the sera of infected molluscs and the qualitative similarities between parasite and host with respect to both free and bound amino acids. Negus (1968), working on Turritella communis infected with the sporocysts of Cercaria doricha, described an almost identical qualitative composition of both the free amino acid pools and the hydrolysates of host gonad and parasite tissue. He was of the opinion that this was not coincidental. Considerable quantitative similarities between the free amino acids were also evident. Read, Rothman & Simmons (1963), in discussing cestode metabolism and membrane transport, proposed that it is the molar ratios of amino acids in the host which are important to the parasite and that the amino acid requirement may be more subtle than a simple need for certain components. Indeed, they suggest that this may form one basis for physiological host specificity.

Transaminase activity in homogenates of larval Digenea indicates that alanine aspartic acid, glutamic acid and their α-keto acid analogues could form an important link between carbohydrate and nitrogen metabolism. As few amino acids participate in transamination it is doubtful whether this process plays a major role in protein synthesis.