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.

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.

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.

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.

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.

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.

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. 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. 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.

1. Dirofilaria aethiops Webber, 1955 has been discovered in African monkeys (Cercopithecus aethiops). Adult worms were found in the interfascicular connective tissue, especially in the thighs; microfilariae were found in the blood.

2. The adult worms are morphologically similar to other members of the genus, from which they differ principally in the structure of the spicules of the male worms. The thickening of the left spicule is complex at the twist; the latter is nearer to the proximal than to the distal end. The right spicule is robust and ends in a cap-like structure.

3. The microfilariae are indistinguishable from those of other members of the genus.

4. In Dirofilaria schoutedeni Vuylsteke & Rodhain, 1938 the left spicule is simpler in structure than the left spicule of D. aethiops, and the twist is nearer to the distal end than to the proximal end. The distal part of the right spicule of D. schoutedeni has longitudinal markings but no cap.

5. D. aethiops has been recorded from Tanganyika, Uganda and Gambia, in Cercopithecus and Colobus monkeys.

6. The anatomy of the female D. aethiops, as it is shown in serial sections, is briefly described.

1. An account is given of the stages of the life history of Dirofilaria aethiops which take place in the monkey and of the transmission of the infection in the laboratory.

2. The microfilariae exhibit nocturnal periodicity in the blood; the number of microfilariae at midday was usually less than 1% of the number at midnight.

3. Aëdes aegypti mosquitoes were fed on monkeys during the evening when there were many microfilariae in the blood. Larvae developed in these mosquitoes and they were ultimately transferred to fresh monkeys by injection of a saline suspension of mosquitoes and infective larvae. In this way six Cercopithecus aethiops and one Macaca mulatto, monkey were successfully infected; seven other Cercopithecus aethiops, one Cebus apella, and one Cercocebus monkey were inoculated, but the worms failed to establish themselves.

4. In the infected monkeys microfilariae appeared in the blood 11 months after the injection of infective larvae. The number of microfilariae then increased for 8–12 months. Subsequently, it decreased to one-tenth of the maximum in 2 years from the first appearance.

5. Post-mortem examination showed that the adult worms live in the fascial tissues on or between the muscle bundles, especially those of the thighs. Tissue reaction to the worms is slight and in these monkeys there was no other pathogenic effect of the infection.

6. Adult worms from three of the monkeys were transplanted to two normal monkeys. Microfilariae were found in the blood of one of these and persisted for over 2 years.

1. A description is given of the morphological development of the larval stages of Dirofilaria aethiops in the mosquito Aëdes aegypti.

2. The first-stage larvae migrate from the stomach to the connective tissue in all parts of the mosquito body, where they pass through the inactive ‘sausage’ stages. At 26° C. and 80% relative humidity the first moult takes place about the twelfth day of development and the second moult about the sixteenth day. The third-stage larvae migrate towards the proboscis where they can be found after 18–20 days.

3. The number of microfilariae ingested by the mosquito is approximately equal to the number which would be expected from the numbers in the blood of the monkey and the volume of the blood meal. The death rate of the larvae in the mosquitoes is very high for the first 2 days, but less severe later. Approximately 1% of the ingested microfilariae survive 20 days; at this time two-thirds of the surviving larvae have reached the third stage.

4. Comparison of D. aethiops with other filariae shows that first-stage larvae of different species can often be distinguished by the structure of the tail, which is the same as that of the microfilaria. Second-stage larvae are similar to each other in morphology but develop in characteristic sites in the host. Third-stage larvae differ from each other in the cephalic and caudal papillae.

1. Filarial worms were found in the peritoneal cavity of a monkey (Macaca speciosa) from Bengal. They were identified as Dipetalonema digitatum (Chandler, 1929).

2. The microfilariae were unsheathed and showed a well-marked nocturnal periodicity in the blood.

3. No development of the microfilariae was detected in Aëdes aegypti, A. albopictus, Anopheles quadrimaculatus or An. stephensi, but only a few mosquitoes were observed.

4. Six female worms and one male were transplanted into the peritoneal cavity of a rhesus monkey (Macaca mulatta). Ten weeks later microfilariae were found in the blood of the monkey and they persisted for at least 16 weeks.

5. Filarial worms (Dipetalonema gracile) were discovered in the peritoneal cavity of a monkey (Cebus apella) from Brazil.

6. The microfilariae were unsheathed and were found in the blood. They showed no periodicity.

7. No development of the microfilariae was detected in Aëdes aegypti, A. albopictus, Anopheles maculipennis atroparvus or An. stephensi.

8. No pathological lesions due to either of these worms were detected in the monkeys.

In 1952 and 1953, 798 specimens of Peromyscus maniculatus, Microtus pennsylvanicus and Clethrionomys gapperi were examined for total louse populations. Two species of sucking lice, Hoplopleura acanthopus and H. hesperomydis, were found on these species. H. acanthopus was found almost exclusively on Microtus pennsylvanicus and Clethrionomys gapperi, and Hoplopleura hesperomydis was found almost exclusively on Peromyscus maniculatus.

Contamination appears to account for the apparently abnormal associations. The rates of infestation varied from host to host and from year to year. In general the higher infestations were found on host populations which were stable or declining, and the lower rates were on hosts which were increasing in density. Microtus pennsylvanicus had the highest infestation rate followed by Peromyscus maniculatus, with Clethrionomys gapperi nearly free of lice.

The age of the host apparently had little to do with rate of infestation or population size.

The louse populations were made up of about equal numbers of adults and nymphs. The adult sex ratio was, in each sample, unbalanced in favour of the females.

The average population size varied between sexes of host and years. The male hosts had a higher average population than the female.

1. NR bodies show special affinity for neutral red. They are rounded or irregular in outline, measuring 0·25–12·5µ in diameter.

2. In fixed preparations NR bodies appear as spherical and vacuolated structures.

3. RNA is present in abundance in mature NR bodies, but while DNA is present in variable amount, the Feulgen technique shows that in their very young stage NR bodies are rich in DNA.

4. Glycogen is absent from the NR bodies, but Hale's technique provides evidence that the hyaluronic acid type of polysaccharide is present in them.

5. By Gomori's modified technique the presence of alkaline phosphatase in the NR body was demonstrated.

6. The mature NR bodies multiply by a process of budding. Small buds or spherules rich in DNA infect fresh spermatogonial cells, the latter being converted into the ‘pathological cells’ of Hertig.

The genus Pneumostrongylus was erected by Münnig (1932) to accommodate the species, P. calcaratus, recovered from the lungs of the common impalla (Aepyceros m. melampus) from the Transvaal. Another species, based on the tail piece of a single male lungworm, was described by Dougherty (1945), from the common white-tailed deer, Odocoileus v. virginianus, from North America. The present species, P. ovis, is based on tail pieces of three male specimens which were recovered from bronchioles of sheep and goats at Murree (7000 ft. above sea-level).

1. Oxynema crassispiculum (Sonsino, 1889) has been redescribed and shown to possess two spicules.

2. The genus Numidica Barreto, 1919 has been shown to be synonymous with the genus Oxynema von Linstow, 1899.

3. The genus Oxynema has been redefined and a synonymic list is given of the species that it now contains.

4. Oxynema typicum Kreis, 1940 is considered to be a species incertae sedis.

5. Baylisnumidica petrodromi (Baylis, 1934) has been redescribed and shown to belong to the genus Parasubulura Berghe & Vuylsteke, 1938.

6. The family Parasubuluridae is reduced to subfamily rank, and placed in the family Subuluridae.

An account is given of the bacterial flora isolated from the blood-sucking Reduviid bugs, Triatoma infestans and T. protracta, and the predatory Reduviid, Sinea diadema. The micro-organisms which have been found in Triatoma spp. differ from that found in Rhodnius prolixus (Actinomyces rhodnii), in both specific identity and in their relation to the cells of the mid-gut. The symbiont occurring most frequently in T. infestans has been identified as a diphtheroid organism resembling Coryne-bacterium hofmannii, and sections show this organism inside vacuoles within some of the endothelial cells of the insect's intestine. The organism occurring in R. prolixus, on the other hand, cannot be found in this situation, but remains in the lumen of the gut. While the occurrence of the bacteria found in T. infestans in so intimate a connexion with the cells of its host seems to suggest a more highly organized state of affairs, T. infestans does not show the fixed association with one species of micro-organism which is shown by R. prolixus. Other bacteria occur commonly in T. infestans, although they do not occur in cell-vacuoles; and the range of bacterial types is so great that it seems unlikely that the species recorded in this paper are the only ones that may occur. The presence of these other bacteria may be due either to the anti-biotic action of the Corynebacterium sp. being weaker than that of A. rhodnii, or to masking of the anti-biotic action by the cell wall that encloses the organisms. The situation in R. prolixus shows clearly that a constant symbiotic association with a micro-organism can be maintained without the presence of specialized organs of the mycetome type.

With regard to the predatory species, no general conclusion can be reached on the evidence so far available. Compared with the blood-sucking Reduviids, insects of this kind usually have powerful proteolytic enzymes secreted in the anterior mid-gut, while the same region of the blood-suckers is a simple storage and concentration sac, digestion taking place lower down the intestine. Thus the region of the gut where bacteria are found in blood-suckers might not be a favourable situation for them in predatory bugs. Hence it is perhaps significant that most of the few successful isolations from a predatory type were from the rectum of the insect. It is the usual opinion that insects with a predatory diet do not need bacterial symbionts, but the aim in examining the predatory Reduviidae has been to find out whether they show a condition which might have evolved into that found in their blood-sucking relatives. The search is still in progress for a rather unspecialized type of predatory Reduviid in which the salivary and anterior mid-gut digestion is less strongly developed than in those species which have been available for study up to the present.

Toxoplasma ‘Nicolle et Manceaux’ has been examined in the electron microscope in in toto preparations from tissue cultures.

The extracellular as well as the intracellular forms of the parasite are too thick for an adequate penetration of the electron beam, and the inner structure of Toxoplasma is not revealed in these preparations.

The whole parasite is covered by a very delicate, transparent mantle which may extend to form large membranes. They show no structure in the electron microscope. No sheath has been observed which protects the shape of the parasite. Most of the free forms have an irregular surface and tend to become flat and large.

Several pictures illustrate the way in which Toxoplasma penetrates the tissue cells. In the beginning of parasitism the limits between cytoplasm and parasite are difficult to recognize. The region of the cytoplasm around the parasite is gradually dissolved and a vacuole is formed.