P. gallinaceum was cultivated in tissue cultures for 1 year. The cultures showed the same high-grade infection as has been observed previously with Toxoplasma and Trypanosoma cruzi, and made possible new observations upon the living parasite.

It has not been possible to obtain in vitro the passage from the exo- into the endoerythrocytic form.

The parasites can survive in tissue cultures, maintained at room temperature, for 23 days.

Observations concerning the periodicity and the phases of the cycle in tissue cultures are being investigated.

An account is given of the technique and interpretation of a test which can be used for the detection of anthelmintics active against threadworm (Enterobius) in man and a number of the helminth infections in herbivorous animals.

It can also be used for the qualitative comparison of active compounds.

It has been used to investigate some of the fundamental practices in the use of anthelmintics—the results of which are to be published elsewhere.

Detailed accounts of the morphology of the elephant louse and of its phylogenetic affinities and origin are given. The main points noted are: The peculiarity of the knobs and plate in the head are described. The mouthparts are described, a notable feature being the rotation of the mandible to 180 degrees. Structural peculiarities of the thorax with the muscles are given. The abdomen is found to consist of eight segments. The alimentary canal is described; no crop has been found. The histology of Weber's organ is given, and it is held that this organ is excretory in function. The structure of the spiracle is described, no spiracular gland has been found. The reproductive organs are described. In the female, the follicular epithelium of the ovary is binucleate and a spermatheca is present. In the male, the testis is bi-follicular. The affinities of the elephant louse are discussed and the creation of a new order, the Rhyncophthiraptera, to accommodate Haematomyzus, is suggested.

A technique is described of the use of two infections in the rat which respond to the anthelmintics acting on a very wide range of gastro-intestinal nematodes. It can be used as a routine screening test for anthelmintics or for the study of variations in the degree of activity caused by alterations in formulation or presentation.

A wide variety of nematode species have been observed to invade the central nervous system. They may be located in the meningeal spaces or may penetrate into the tissues of the brain and spinal cord.

The pathological changes resulting from invasion of the central nervous system are influenced by the route of entry, the size and the mobility of the parasite. They may be diffuse or focal and may include haemorrhage, degenerative changes, cellular infiltration and glial proliferation. Such changes may or may not be observed in close association with the parasite.

Symptoms indicating involvement of the central nervous system have long been associated with nematode infections outside the central nervous system. The pathogenesis of these symptoms is obscure, but they may possibly be of allergic origin.

The direct pathological effects on the central nervous system are mainly the result of trauma and are directly proportional to the size and activity of the parasite. The possibility that nematodes may transport viruses into the central nervous system is briefly discussed.

1. A controlled taeniacidal technique is described using mice artifically infected with Hymenolepis nana var. fraterna.

2. The method of interpretation is based upon a form of computation relating to the number and sizes of worms left in the treated animals as well as the proportion of mice rendered negative by the treatment as compared with untreated controls.

1. Experimental infections in mice showed that the larvae of Toxocara canis, T. mystax, Ascaris devosi, A. columnaris and Toxascaris transfuga reached the brain of mice; the larvae of Ascaris lumbricoides, A. suum, Parascaris equorum and Toxascaris leonina were not recovered from the brain. The larvae of T. canis, T. mystax, T. transfuga and A. columnaris remained hi the brain of mice for several months.

2. Larvae reaching the brain produced characteristic haemorrhages on the surface of the cerebral hemispheres in the early stages of infection. It was concluded that the larvae reach the brain via the arterial blood stream, leave the arteries at the point where their diameter approximates that of the larvae, i.e. mostly on the surface of the brain, and penetrate into the brain from the subarachnoid space and chorioidal tissues.

3. The larvae of T. canis were found to occur in the brain of mice in relatively greater numbers than the larvae of other species, but only very rarely caused nervous symptoms. The larvae of T. canis and T. mystax showed no growth in the brain.

4. The larvae of A. columnaris (skunk) frequently caused nervous symptoms in mice, the effect appeared to result from traumatic damage due to the relatively large size attained by these larvae about 3 weeks after infection.

5. The brain of infected mice showed very slight changes consequent upon infection with larvae of T. canis. These larvae moved actively through the tissues; they incited little or no cellular reaction, but left haemorrhagic tracks. The larvae of A. columnaris also moved actively; when in the extended state they were usually found in normal tissue; when coiled, they were often associated with a necrotic focus infiltrated with leucocytes.

6. After experimental infections of dogs with larvae of T. canis, two out of twelve infected animals harboured larvae in the brain. No natural infections with these larvae were found in the brains of dogs and cats. After experimental infection, larvae of T. canis were found in the brain of mice, rats and guinea-pigs, but not of rabbits.

7. Larvae of A. suum were recovered from the cerebrum of one pig suffering from posterior paralysis, but not in an experimentally infected pig.

8. No larvae of P. equorum were found in the brain of foals in natural and experimental infections.

It has long been customary to use a single large dose in the treatment of worms in animals, but in man there has been a tendency to use a course of doses, especially in the treatment of threadworm. In the case of phenothiazine when used against threadworm the division of the dose has probably been undertaken in order to avoid toxicity. There is, however, no definite evidence that the toxic hazard is reduced in this manner, in fact, it may well be increased as with poorly absorbed substances greater absorption is obtained with the presentation of the treatment over a longer period. This can be clearly demonstrated in laboratory tests.

Wild Stomoxys calcitrans flies were dissected in search of developmental larvae of Setaria cervi without success.

S. cervi worms were implanted intraperitoneally into rabbits and live microfilariae were recovered from the blood.

Morphological descriptions are given of the larvae from the blood of rabbits and of the adult worms taken from slaughtered cattle.

A male specimen of the monkey, Cercopithecus aethiops pygerythrus (Cuvier), caught near Bedford, Eastern Cape, was sent to us by Dr P. A. D. Winter of the Polio Research Foundation, Rietfontein. On arrival at Rietfontein this monkey showed slight symptoms of a mange, described by Dr Winter as follows: 'The lesion was scaly with underlying patches of erythema. Over the lesion the hair was thin. On scraping, much of the scaly material could be taken away, revealing irregular, raised erythematous patches. These patches were distributed particularly on the dorsal aspects of the limbs and there were also several of them on the chest, abdomen and head.

The genus Paradilepis Hsü, 1935 syn. Meggittiella Lopez-Neyra, 1942, is defined as follows (Hsü, 1935, p. 536): ‘Dilepididae. Rostellum armed with a double crown of hooks. External segmentation little marked. Genital pores unilateral. Genital ducts pass dorsal to excretory vessels and to nerve. Testes few in number, situated to either side of the female glands. Uterus sacciform, little lobed. Parasites of birds.’

Claparède (1869) established the genus Myocoptes for a mite, found upon a house-mouse (Mus musculus musculus L., 1758), which had been described by C. L. Koch (1844) under the name Sarcoptes musculinus (syn. Listrophorus larisi Vorobiov, 1938). In this genus sexual dimorphism is pronounced; the female has legs iii and iv modified and provided with processes with which it can maintain a firm grasp on the fur of its host. In the male this modification is only present on legs iii.

The new species of Trypanosoma described in this paper is parasitic in the blood of Ophicephalus ( = Ophiocephalus) striatus Bl., an air-breathing teleostean ‘Serpentfish’ found extensively in the fresh waters of India. This fish is one of the important food-fishes of India, especially in areas far away from the sea, which are mainly served by inland fisheries. It is equipped with an elaborate accessory air-breathing organ and therefore survives when taken out of water and kept in a moist condition. This hardiness of the fish has made it a popular item of diet since it is available in the hottest months of the summer in a fresh condition or even alive. With the expansion of the inland fisheries of India the importance of fishes of the genus Ophicephalus is also on the increase.

1. Extracts made from whole nematode worms, Litomosoides carinii, and from Ascaris ‘heads’ and body wall tissue, contain a substance similar to acetylcholine.

2. In the case of extracts from Litomosoides whole worms, this substance was shown to be probably acetylcholine itself.

3. Tissue from the anterior end of Ascaris (including the nerve ring), contains about 15 times as much acetylcholine as the body wall preparations; i.e. 0·39μg./g. as compared with 0·025μg/g. of wet weight.

4. There appeared to be rather more acetylcholine present in the Litomosoides males than in the females; 0·92μg./g. as compared with 0·63μg./g. of wet weight.

5. The microfilariae of the filariid nematode of the dog, Dirofilaria repens, contain as much as 2·4;μg./g. of acetylcholine. In this respect it resembles some other motile parasites of the blood, such as trypanosomes.

1. Spores of Nosema apis nearly all germinate within 30 min. after entering the ventriculus of the honeybee.

2. The cause of germination in vivo remains unknown, but is probably not a change of osmotic pressure or pH and is probably not due to anaerobic conditions or an enzyme. The agent causing germination is probably unstable and is destroyed when removed from the bee.

3. The anterior end of the ventriculus receives an initial heavy infection and the circumstantial evidence which this provides supports the theory that a free living ‘planont’ stage does not exist but that the parasite is injected directly into the host cell from the spore via the hollow polar filament.

4. The central region of the ventriculus which contains many granules of calcium phosphate receives the lowest initial infection. It is considered possible that the granules inhibit the initial rapid development of the parasite by maintaining an unfavourably high level of pH until they are eventually dissolved by the slowly developing organism.

1. Large numbers of minnows (Phoxinus phoxinus (L.)) from Fron Goch Pool, near Aberystwyth, have been found to be heavily infested with Diplostomulum pelmatoides Dubois ( = D. phoxini (Faust)), the parasites occurring in very large numbers in the brain, spinal cord and eyes.

2. The excretory system of the worm has been worked out in detail. There are fifty-two pairs of flame cells.

3. Infested heads, brains and eyes have been fed to the domestic duck and the adult stage of the worm Diplostomum pelmatoides Dubois obtained.

4. Some morphological details of the adult worm are described.

5. The natural bird host of the parasite in this country is not yet known, nor the stages in the molluscan host.

1. Cerfontaine's (1896) description of the egg is confirmed. The eggs are not retained on the gills during development.

2. Maturation of the oocyte takes place after egg formation. The haploid number of chromosomes is 9.

3. The onset of embryonic development is related to the time of egg formation or sperm entry. Cleavage is total and slightly unequal, leading to the formation of a morula in which there are no germ layers. The larval gut is formed by epiboly round a mass of yolk which becomes incorporated in mid-body. Larval organs and a partially ciliated epithelium are differentiated in situ.

4. During embryonic development yolk is broken down and absorbed, some being incorporated in the body.

5. Hatching does not seem to result from any special stimulus. Mechanical pressure by the larva forces off the operculum, but secretions may weaken the suture.

6. The free-swimming larva is gyrodactyloid with a winged haptor bearing four pairs of lateral, one pair of postero-lateral and one pair of median hooks. Four pairs of flame cells are present and one pair of longitudinal, lateral, excretory ducts, which open antero-laterally. The larva swims by ciliary action and does not respond to jarring, light and shade stimuli, or, when vigorous, to the presence of the excised gill of the host. Tired larvae are doubtfully attracted by host gill tissue. Larval haptorial type is thought to be determined phylogenetically rather than as a result of adaptation to the type of host tissue to which the larva attaches itself.

7. The larva attaches itself to the host's gill and sloughs off the ciliated coat. Growth follows with the development of the adult clamps in pairs, starting posteriorly, each pair replacing a pair of lateral, larval hooks. Primordia of the reproductive organs are laid down in the larval stage, but are only finally elaborated when the adult form has been attained. Maturity is not reached at a definite size and the ovary and testes mature simultaneously.

8. Feeding is at least partly on the host's blood.

9. The longest time which may elapse between formation and laying of an egg is about 5 hr. The average time taken for embryonic development is 18·3 days at 14·25° C., but temperature affects the developmental rate. Ciliated larvae survive about 24 hr. in the absence of a host. The second larval stage is reached between 5 and 13 days after hatching, the third larval stage after more than 38 days. The immature stage is thought to be reached within 3 months and the adult stage within 6 months.

10. Reproduction occurs throughout the year. The animal is functionally hermaphrodite at all times once maturity is reached.

11. A certain degree of osmo-regulation is possible in adults, but this does not extend to ciliated larvae.

12. Adults rest along a gill filament on its inner face and do not move about. Larvae are more ready to move.

13. The average number of flukes per host is 2·24. The 1st and 2nd pairs of gills carry three times as many flukes as the 3rd and 4th pairs.

14. The host suffers no apparent harm from the presence of the flukes.

15. Premunition of Gadus virens against Diclidophora denticulata does not occur. Age resistance is probably developed to the extent that larvae cannot establish themselves on older fish and is probably due to mechanical difficulties and changed habits of the host. The ability of this fluke to parasitize species of Gadus does not extend to G. callarias.

16. D. denticulata is recorded for the first time from St Andrews Bay and the Firth of Forth.

1. The larva and nymph of Rhipicephalus pulchellus are described for the first time and comments are made on the degree of variation in structure seen amongst adults of a single generation.

2. Information on various aspects of the biology of this tick and on classification is given.

1. A review is given of the Laelaptid paraphages of the Myriapoda with a key to the genera.

2. One new genus, Scolopendracarus (type: S. brevipilis) and a new subgenus, Parajacobsonia (type: Jacobsonia tertia Vitzthum) of the genus Jacobsonia Berl. are proposed.

3. The following three species are described as new to science: Jacobsonia (Jacobsonia) audyi, Scolopendracarus brevipilis, Hypoaspis (Hypoaspis) polydesmoides.

4. The phylogeny and classification of the family Laelaptidae Berl. are discussed. A key is given to the subfamilies of the Laelaptidae.

This work started in May 1950 and is part of a wider study of parasite populations on lowland pastures.

An account of observations made on ewes has already been given (Crofton, 1954), and the present paper deals with observations made on lambs from the same flocks. It is realized that a proper approach to parasite problems in sheep entails consideration of the flock as a whole, but for convenience, the observations made on different age groups have been described separately. It is for convenience, also, that pasture contamination is only considered briefly here. Later an attempt will be made to consider parasite populations on a lowland farm as a dynamic system of interacting factors.