The small group of Trematodes here discussed comprises new species of the genera Megalocotyle, Calicotyle and Microcotyle.

Trichomonas sp. from a corais snake

Description. Body usually pear-shaped. Average size 12 × 8μ, Three anterior flagella of unequal length. Basal fibre absent. Feebly developed undulating membrane.

Habitat. Intestine of Dymarchon corais, from North America.

Locality. London.

In this section are collected all the instances recorded at this laboratory of the testing of T. gambiense on man, after the trypanosome had been maintained for a time in laboratory animals.

Of the five species of helminths of the British muskrat (Ondatra zibethica L.), two (Notocotylus quinqueserialis and Hymenolepis evaginata) have been introduced with the animal. The three other species of helminths (Capillaria hepatica, Taenia taeniaeformis larva and T. tenuicollis larva) have probably been largely re-acquired from the local fauna. All of the three common species of ectoparasites [Laelaps multispinosus (Tetragonyssus spiniger), Listrophorus validus and Dermacarus n.sp.] occur in North America. Three other species (Tyroglyphus sp., Myobia n.sp., Polyplax sp.) have occurred as single individuals, the last species having probably been acquired from the water vole. Introduction into Britain has greatly depleted the original helminth fauna as regards number of species and individuals; but not so with the ectoparasites. Lists of the parasites hitherto recorded from the muskrat are given and those found in brown rats (Rattus norvegicus Erx.) and water voles (Arvicola amphibius amphibius L.).

A Eutrichomastix morphologically identical with E. serpentis (Dobell, 1907) Kofoid & Swezy, 1915, is described from 3 species of African snakes, namely, Psammophis sibilans, Boaedon lineatus and Crotaphopeltis hotamboeia.

Many biologists are at present interested in populations of animals, which are studied experimentally and also by more abstract mathematical methods, but it is frequently difficult to obtain facts about actual populations living under natural conditions unless they are studied by sampling, the accuracy of which cannot always be precisely defined. The method described in this paper tells us of the actual numbers of headlice in crops of hair on individual people. From it we may learn the proportion of people who are infested at different times or places, and the number of lice on different people: also the proportion of males, females and young in the louse population. The results with material from Woolwich and from Lagos are set out in this paper. Further work is now in progress on material received from several parts of the world: this material will be studied and the results published at a later date.

This paper is devoted to a critical analysis and revision of the systematics of the mammalian trypanosomes. It is shown that there is no justification for the recognition of more than one genus, Trypanosoma.

The trypanosomes are subdivided into two sections, each with distinct morphological and biological characteristics.

In the section corresponding to the lewisi group the method of reproduction is used as a criterion for the specific differentiation of the trypanosomes.

1. Experiments upon Xenopsylla cheopis Roths. are described which were carried out to discover if feeding influenced duration of life or had any effect upon the survival of the sexes or upon the relationship between duration of life and saturation deficiency of the atmosphere.

2. Fleas fed once before starvation lived longer than unfed fleas. There was no difference between survival of the sexes and no direct proportion between survival times and saturation deficiency.

3. Fleas kept with the host for 7 days before starvation lived still longer. Females lived considerably longer than males, but there was still no direct proportion between survival times and saturation deficiency.

The morphology and life cycle of an amoeba producing amoebiasis in reptiles is described. The organism is assigned to the species Entamoeba invadens Rodham 1934, because of the pathogenicity of that species.

Material for the study was derived from 30 individuals of 7 species of reptiles, either dying of spontaneous amoebiasis or experimentally infected. (Material from 3 additional species of reptiles dying of amoebiasis was not used in this study.)

With the exception of a few minor morphological differences, E. invadens was found to be strikingly similar to E. histolytica in morphology of trophic and cystic stages, and in the processes of encystation, excystation, and metacystic development.

Metacystic development was studied in stained preparations made from the intestines of snakes 1–24 hours after the inoculation by mouth of mature cysts. Excystation usually takes place in the jejunum and ileum, a single quadrinucleate amoeba hatching from each cyst. Each quadrinucleate metacystic amoeba ultimately forms 8 amoebulae as a result of one division of each cystic nucleus, cytoplasmic division, and parcelling out of the cystic (N) and daughter (n) nuclei. Nineteen of the 24 possible combinations of N and n nuclei were observed.

The culture phenomena of multiple fission without encystment is suggested, and cannibalism of cysts by the trophozoites is described.

The following animals are from a collection made for and kindly presented to me by Miss Miriam Rothschild during her visit to Brighton in July and August 1935.

The description of Sphyranura oligorchis (Alvey, 1933) and S. polyorchis n.sp. is presented together with an account of the development of the former. Study of the life history of S. oligorchis, and a review of the literature on the life cycles of the Monogenea, show that at a corresponding time in their development embryonic stages similar to Dactylogyrus are present. It is postulated that Dactylogyrus is near the primitive ancestral type of the Monogenea, and that all of the parasitic platyheminthes may have arisen from a common planula ancestor.

1. Examination of monthly quotas of Apodemus sylvaticus, Clethrionomys glareolus, and Microtus hirtus, for parasites over a period of 21 months, enabled the seasonal occurrence of Trombicula autumnalis larvae to be determined.

2. All three species are infested during the summer and autumn months, and Clethrionomys throughout the following winter and spring also. Shrews were not parasitised.

3. The mites occupy different positions on different hosts.

4. Clethrionomys and rabbits (Oryctolagus) are of importance in maintaining the stock of harvest mites on some areas in the south of England.

1. A specific disease of cattle is described which occurs sporadically in the East Coast fever areas of eastern equatorial Africa. Clinically, acute cases are characterised by peculiar nervous symptoms, absence of fever and blindness. Death occurs in most cases within 2 to 21 days of the onset of illness. Chronic cases are encountered from time to time and may survive up to 6 months.

2. The disease is widespread in Uganda. It affects cattle of both sexes and all breeds, and is commonest in young stock between 6 months and 2 years of age. It has, however, been observed in older animals.

3. Pathologically, in acute cases petechial haemorrhages or extravasations are found in various parts of the brain and meninges. Generally the haemorrhages are small and do not seriously injure the adjacent brain tissue. In some cases the extravasations are responsible for a considerable amount of damage.

4. Microscopic examination shows that the brain lesions are due to extensive embolism of cerebral vessels. The lymphocytes which form these emboli contain in their cytoplasm protozoan bodies indistinguishable in structure from the schizonts of the genus Theileria. These bodies occur in great numbers in the brain, but are extremely rare or absent in the lymphocytes of other parts of the body.

5. In chronic cases the haemorrhages have been absorbed but the brain is permanently damaged by replacement changes, and by the appearance of small cysts or cavities which contain a citron-coloured fluid. These cavities when numerous seriously disorganise certain parts of the brain.

6. The disease has not yet been transmitted experimentally, and its connection with the theileriases is still uncertain. However, much evidence has been collected to show that cases of turning sickness have been infected with East Coast fever some time previously, generally on an average of 6–8 months.

7. The possible relationship between turning sickness and East Coast fever is discussed at some length during the course of the paper.

1. An English anautogenous race and three European strains of the autogenous race of Culex pipiens have been studied comparatively for 3 years under laboratory conditions.

2. Prolonged illumination has an activating influence on females of the anautogenous race, both hibernating and laboratory bred, and greatly stimulates gorging.

3. With the aid of artificial light during the winter months the anautogenous race has been kept breeding in the laboratory throughout the year for eleven generations without the occurrence of cyclical hibernation (asthenobiosis). Consequently it is suggested that the length of daylight may be a factor of importance in controlling the natural hibernation of females of this race.

4. Females of the English anautogenous race, whether of hibernating, or of active generations, laid normally after one blood meal and did not exhibit gonotrophic dissociation. They also oviposited readily after being artificially fed on bird blood.

5. Unfed females lived for a maximum of 19 days and never accumulated fat-body autotrophically.

6. Females, if fed on apple for 5 weeks, accumulated sufficient reserves to enable a small percentage of them to survive 15 weeks of starvation.

7. In the anautogenous race pairing always begins in the air although it may be completed on the ground. The females do not lay without a blood meal, and they show little tendency to bite man but bite birds voraciously.

8. Strains of the autogenous race of C. pipiens were obtained from rural areas in Greece, Malta and Hungary and have been maintained in the laboratory for over 3 years.

9. Continuous breeding under autogenous conditions (no blood meals) for several years and through forty-five to forty-nine generations has had no deleterious eflect on these autogenous strains.

10. Spanogyny, or the gradual decrease in the numbers of females produced in succeeding generations, does not necessarily follow prolonged autogeny if the cultures are kept under favourable conditions.

11. Males of the autogenous race pair with resting females, so that pairing can take place in very small areas.

12. Cross-mating was easily obtained between the two races, autogenous and anautogenous, in both directions: male autogenous + female anautogenous; and male anautogenous + female autogenous. Stenogamy and autogeny are hereditary characters. Stenogarny always appears in the F1 generation, but autogeny sometimes appears in the F1 generation and sometimes not until the F2 generation.

13. Eggs are quickly killed by temperatures below freezing-point; and young larvae die within 24 hours at 0° C. Adults, even hibernating females, die within 4 days at −16° C.

1. A detailed description is given of a coccidian which parasitises the nuclei of the intestinal cells of the polychaete worm Polydora flava Claparède. The final stages in sporogony have not been observed; nevertheless, this is the first record, from an annelid worm, of an eimeriid which shows a striking resemblance to those Coccidia occurring in the higher animals. It is also the first record of an intranuclear parasite from an annelid.

2. From the gut of the same worm, a new species of Selenidium is described. It differs from all other species, hitherto recorded, in the possession of an axial tube, which completely encloses the nucleus and extends from one end of the organism to the other: hence it is proposed to name this organism Selenidium axiferens. The anterior end of the trophozoite shows a circlet of siderophilous bodies, which Ray (1930 a) has shown to be characteristic of the genus.

3. Both uninucleate and multinucleate intracellular forms, with polar groups of chromatic globules, have been discovered in great abundance on six occasions; no merozoites have been found, but evidence is submitted to show that these intracellular forms represent the schizogonic phase in the life-cycle of the Selenidium.

4. Sporogony follows closely that described for other species, but the final stages have not been observed. The gametocysts measure 48 × 50–70 × 63μ.

5. Association and cyst formation are described in Polyrhabdina polydorae Caul. & Mesn. (?) for the first time. Innumerable nuclei make their appearance in each gametocyte, before ejection of the cysts into the sea-water takes place. Gametocysts can easily be distinguished from those of Selenidium axiferens, not only by their morphology, but also by their greater size (98 × 90–105 × 100μ).

A bacterial organism is described which occurs constantly in Rhodnius prolixus. It is present in the unfed newly hatched insect inside the cells at the cardiac end of the mid-gut. Some days after feeding, the bacteria are set free into the cavity of the gut and multiply in the undigested blood in the stomach. They are ultimately digested in the intestine.

Morphologically they resemble diphtheroid bacilli in being highly pleomorphic and in giving rise to thread-like forms in old cultures.

Preliminary experiments with Lucilia larvae by Dr R. P. Hobson, suggest that when blood is infected by this micro-organism it contains “vitamin B” and becomes an adequate diet for insect growth.

These observations support the view that symbiotic organisms in exclusively blood-sucking insects provide an endogenous source of vitamin.