In March 1932, while examining the gut contents of Bufo melanostictus, I came across a species of coccidian in two specimens. On consulting the literature, I found that while five species of Eimeria have been recorded from the intestinal region of anurous amphibians, none of them corresponds with the one I have observed. Moreover, I notice that for no one of these five species has the whole life history been described.

ON 19. v. 1934, while trawling from S.S. Salpa, kindly placed at my disposal by the Marine Biological Association, Plymouth, the following Lernaeidae were taken:

1. Chilomastix from Bufo vulgaris has been grown in culture media but a “pure” strain was not obtained. Division and encystment occurred.

2. Two types of division were found. In one type the original cytostome and flagella persisted and a new set was formed from one pair of basal granules. In the other type the original cytostome disappeared and two new ones were formed from the two pairs of basal granules. This second type of division is similar to that of Chilomastix aulastomi from Haemopis sanguisuga.

3. It is therefore probable that two species of Chilomastix are present in Bufo vulgaris.

4. Cysts of Chilomastix from Bufo vulgaris and of Chilomastix aulastomi were studied. Nuclear division was never seen in them.

I wish to offer my best thanks to Mr Clifford Dobell, F.R.S., for kindly reading through the manuscript.

A second species of the genus Endorchis is described—E. mandubé; also new species of the rare genera Monticellia, Amphoteromorphus and Nomimoscolex, viz. Monticellia piracatinga, M. rugosa, Amphoteromorphus parkarmoo, Nomimoscolex piracatinga and N. kaparari.

A new genus Manaosia is created to contain the anomalous species M. braço de moça. Proteocephalus lenha becomes Nomimoscolex lenha.

The species Spatulifer surubim, originally described by me as Peltidocotyle rugosa and later referred to the Amphilaphorchidinae, is now regarded as a species of the Monticelliinae.

The eight known species of the Monticelliinae are all referred to the single genus Monticellia, since, differences in vitellaria distribution not corresponding to differences of scolex form, the only alternative is to create an unnecessary number of genera. The genera Goezeella Fuhrmann and Spatulifer Woodland are thus regarded as superfluous.

“Ephedrocephalus” lobosus is removed from the Ephedrocephalinae (which retains its single species E. microcephalus) and, with the two species of “Amphilaphorchis” recently described by me, is placed in Fuhrmann's genus Rudolphiella, now re-established, in the subfamily Rudolphiellinae, thus replacing the Amphilaphorchidinae.

The complete list of known subfamilies, genera and species of the Proteocephalidae described from the Amazon, amended in accordance with the above conclusions, has been published in my last paper on the subject (Woodland, 1935).

In October, 1934, several specimens of a tick belonging to the genus Ornithodoros were forwarded to the Bureau of Animal Industry for identification by Drs William Thompson and N. E. Dutro. These ticks were first observed by Mr F. E. Swan of the Bureau of Entomology and Plant Quarantine in a carload of bat guano originating at Linares, Mexico, and held in quarantine at Matamoros, Mexico.

The family Fellodistomidae Nicoll 1913 comprises two subfamilies, Fellodistominae Nicoll 1909 and Haplocladinae Odhner 1911, which are composed of a large number of genera of small flukes, all parasitic in fishes. The type genus of the family was described by Stafford in 1904 from the gall bladder of a Canadian wolf-fish, Anarrhichas lupus. Subsequently several new genera have been added from European and American fishes, but until now no representative of the family has been reported from India.

Large populations of the new species of Entodinium were found in 27 out of 120 stomachs (from the paunch to reticulum) of Bos taurus from various regions of Yugoslavia. The stomach content was fixed in 4 per cent. formaldehyde. Unstained glycerine mounts and material stained in iron haematoxylin and Mallory's phosphor-molybden haematoxylin were used. Twenty individuals from each population, i.e. 540 individuals in all, were measured. The length was found to vary from 26·25 to 38·5μ, and the width from 24·5 to 31·5μ. The relation between the length and the width was 1·16, which indicates the average degree of rotundity. This rotundity, especially noticeable in individuals in which the adoral membranelle zone is retracted, may sometimes be less pronounced at the anterior end. Entodinium bovis is considerably flattened, so that its thickness does not exceed 6–10μ. The pharynx is curved dorsally. The cuticle is longitudinally striated. The ectoplasm is more developed in the anal region than laterally. The macronucleus is elongated, 10·5–21 × 3·5–5×25μ, and is thicker at its anterior end. The micronucleus is round and lies ventral to the macronucleus at a point about the middle of its length. The contractile vacuole lies ventral to the macronucleus, near to its anterior end. The anus is usually situated in the middle of the posterior end of the ciliate, though sometimes it lies slightly ventral.

The two species of bed-bug, Cimex lectularius and C. rotundatus, are found in temperate and tropical regions respectively. They are very similar anatomically, and have the same habits.

Physiologically, the two species have many resemblances. Their water balance is similar; they are very little affected by humidity if there is plenty of food available. The thermal death-points are identical.

At temperatures below 30° C., C. lectularius is able to breed more rapidly and more successfully than C. rotundatus. Between 30 and 35° C. both species behave alike, and above 35° C. C. rotundatus may be the more efficient species. Under most conditions, C. lectularius is the more resistant to starvation and desiccation.

Results indicate that although C. lectularius is more fitted for life in temperate countries, if introduced into the tropics it should be able to carry on at least as well as C. rotundatus.

Studies of geographical distribution indicate that C. rotundatus has spread all over the tropics, but has never established itself outside them. C. lectularius has spread all over the temperate world, and into the ports in some tropical countries. Experimental work suggests that it may become widespread in those parts of the tropics into which it is introduced.

An account is given of the preparation of Elford's gradocol membranes and their application in the study of plant viruses. The technique is discussed step by step and the chief sources of error are indicated. It is shown that plant virus suspensions clog the membranes, and suggestions are made for the preparation of those suspensions for filtration. The effect of virus content, purification and pH of virus fluids upon their filtration is discussed.

An account is given of an apparently undescribed virus disease. The virus appears spontaneously in the glasshouse affecting tobacco seedlings in the seed boxes. The symptoms on a number of hosts are described. The chief characteristic of the virus is its failure to become systemic in any host plant so far tested. It is, however, occasionally found in the roots of young tobacco plants, usually in the case of those naturally infected. Certain physical properties of the virus have been investigated. Its dilution end-point appears to be about 1:10,000; its longevity in extracted sap is about 20 days, the thermal death-point is 72° C. The virus shows a strong resistance to alcohol, remaining viable in 99 per cent, alcohol for 71 hours so far as tested.

It is not known how the virus is transmitted in nature, and no insect vector has as yet been identified.

The virus has been transmitted to healthy cowpeas by spraying them with a suspension of the virus by means of an atomiser.

By the Elford method of ultra-filtration the particle size is found to be 20–30μμ.

The virus is compared with that of the American tobacco ringspot, and methods of differentiating the two are indicated.

In a previous paper (MacLeod, 1934) the different physical factors in the environmental complex of the sheep tick were discussed in their relation to the development of the gorged tick, and an experimental analysis was made of the effects produced, under laboratory conditions, by their action and interaction. The present paper deals with the active unfed ticks. These present rather a different problem from the gorged ticks, for, whereas in their case the climatic optimum resolved itself into that combination of conditions under which development proceeded favourably and with a low attendant mortality, the unfed tick, on the other hand, is faced with two desiderata, survival and hostparasitisation, the physical optima for which may not be coincident. It is necessary, therefore, to consider not only the climatic optimum for survival and activity, but also the factor or factors which influence parasitisation, and those conditions under which host-parasitisation is facilitated.

The results described above indicate that quinanil and the compound 2 (p-dimethylaminoanil)-β-naphthoquinoline methochloride might be successfully used as selective reagents for the isolation of insect flagellates of the genus Leptomonas.

The actual concentrations, which might be successfully used in the culture media, will show some variation according to whether the flagellate is adapted, at the time, to luxuriant growth in the media used. For example, in preliminary experiments, the Leptomonas from Polietes and Calliphora grew better in Locke serum agar than in bouillon, and quinanil was more toxic in the latter than in the former. In the present experiments the reverse held, but in later ones, not here recorded, where the flagellates have again grown more abundantly in Locke serum agar, growth regularly occurs in 1/6000 concentrations of quinanil in this medium. There is little doubt from other results, not yet published, that some Leptomonas forms can be made to show modification of cultural requirements through adaptation. It is probable therefore that in the attempted isolation of fresh forms from the gut of the insect, several kinds of media might have to be employed.

After this work was completed, in several attempts made to purify laboratory-contaminated cultures, success was attained by following the suggested methods, using quinanil and 2 (p-dimethylaminoanil)-β-naphthoquinoline methochloride. The compound 113 was even less toxic to the Leptomonas forms in media than was the compound 52, but its bactericidal action was correspondingly weaker. The few experiments conducted in the absence of media indicated that this substance might have proved very useful, but unfortunately the material gave out and further supplies were not available. In the preliminary treatment of gut contents, acriflavine, owing to its apparently bacteriostatic action, might prove of some value for destroying organisms of the Bacillus prodigiosus type.

Consideration of the results obtained with gentian violet, brilliant green, and the two anilquinolines, 2 (p-dimethylaminoanil)-6-acetylaminoquinoline methochloride and methosulphate, suggests that these compounds are of no use as selective bactericidal substances permitting the growth of Leptomonas forms. The combined action of two or more of these substances has not yet been studied.

As our results indicate, little success is to be hoped for in this direction with the Leishmania forms, which are extremely susceptible to the toxic effects of all the substances employed. Two points of interest were obtained from these results. It might be noted that Leptomonas ctenocephali reacted in a similar manner to the Leishmania forms but that Leishmania tropica (“Baghdad”) behaved like a Leptomonas form. This strain appeared similar in all respects to the other Leishmania forms, but it was the only one readily acclimatised to media containing no blood. Its morphology also showed some modification after a time.

We are greatly indebted to Dr St John-Brooks, Curator of the National Collection of Type Cultures, and to Prof. S. Adler of the Hebrew University, Jerusalem, for certain of the cultures of Leishmania and Leptomonas used, and also to Dr K. E. Cooper for the gift of the anilquinoline derivatives and for much helpful advice.

One of us (F. C. H.) has also been in receipt of grants from the Medical Research Council, and he would like to take this opportunity of expressing his thanks to that body.

1. The distribution of the larvae of Simulium spp. in the River Tees area is discussed.

2. The dominant species of

(a) the upper Tees are S. monticola and S. variegatum;

(b) the lower Tees are S. equinum and S. reptansvar. galeratum;

(c) the Skerne is S. ornatum.

3. The causes of these differences are unknown, but it is suggested that geological structure, the distribution of water plants and the hardness of the water are important factors.

1. “Trichomonas” keilini n.sp. has three anterior flagella, and a short undulating membrane, whose bordering flagellum does not become free. The flagella arise from an anterior blepharoplast. There is a single nucleus, anteriorly placed, and a mouth, but no basal fibre to the undulating membrane. An axostyle may be present or absent, but when present it is siderophilic. The method of multiplication of “T.” keilini is similar to that of T. hominis and T. batrachorum.

2. “T.” keilini was found in water from a pond in Lincolnshire.

3. It has been cultivated in serum-saline media, in hay infusion, and in pond or rain water with boiled wheat grains, from 4 to 31° C.

4. Cysts have never been found.

I should like to record my gratitude to Prof. Keilin, F.R.S., who gave me the sample of water in which I first saw the organism, and who gave me encouragement throughout this study; and to Mr Clifford Dobell, F.R.S., for the gift of the macaque-human strain of Trichomonas and for so kindly reading through and criticising this manuscript.

Stages of incomplete division of chains of individuals in the species Herpetomonas bancrofti, as well as the distribution of abnormal cells within long chains, were found to support the writer's earlier view (Holmes, 1931) that successive longitudinal divisions of individuals occur within chains. In this type of division there is alternate splitting of individuals from anterior and from posterior ends of cells. It is concluded that this hitherto unproved type of division of pairs and chains is sufficient to account for the presence of all observed aggregates.

No evidence was found suggesting occurrence of any essentially different type of cell division, such as the transverse fission reported by Franchini (1931, 1931 a) as possibly accounting for formation of chains in H. ganorae.

Many workers must have asked themselves whether a malaria parasite of bird or mammal has any harmful effect on the mosquito in whose body it grows and multiplies so remarkably; but though various opinions have been expressed, I cannot discover that any conclusive answer to this question has been given.

1. Perispiracular glands are present in the larvae of Anopheles and Culex.

2. These glands secrete an oily substance which is responsible for the hydrofuge properties of the spiracular region of mosquito larvae.

3. The differential wetting of the spiracular region and the action of oil on mosquito larvae depend on the presence of this oily secretion.

1. The life history of Merocystis kathae shows that development follows a seasonal course. The youngest stages may appear in the kidney any time between March and June. Growth proceeds and sexual differentiation takes place but mature gametes are not found until November, when the first stages of sporogony also make their appearance. Mature spores containing sporozoites are formed in January and become increasingly common up to May. Degenerating stages of spores are common in summer.

2. The smallest parasites within the cells of the kidney are about 10μ. Growth occurs in the intracellular condition. The karyosome is complex, and contains a chromatinic body; in older parasites no chromatin reaction is given by the nucleus outside the karyosome.

3. Sexual differentiation is not perceptible until growth is almost complete.

4. In the female the intrakaryosomic body emerges, though a large karyosomic remnant remains until after fertilisation. Very fine granules of chromatin reappear in the nucleus, and form a fine network, which incorporates the intrakaryosomic body, and later forms the characteristic prefertilisation ‘cobweb’ nucleus. This network contracts in the mature macrogamete. Meantime the parasite has become free of its host cell, and the cytoplasm stains more intensely.

5. In the male, the elongated karyosome breaks down, generally completely, leaving the centrally placed chromatin body surrounded by a ring (in sectional view), of deeply stained material containing granules of chromatin, into which the central body passes as in the female. The male is released from the host cell, and, as in the female an alteration of the cytoplasmic staining occurs.

6. The nucleus, in the male parasite, moves to the surface, and undergoes repeated divisions until approximately 32 nuclei are formed. Cleavage of the cytoplasm brings about the formation of uninucleate cytomeres; within each of these are produced many nuclei, which lie near the surface, and finally become the microgametes.

7. After the macrogamete is fertilised, a thick membrane is formed outside the zygote. The nucleus assumes the characteristic spindle shape and subsequently divides.

8. Nuclear divisions proceed, until finally a great number of cone-shaped nuclei are found on the surface. This becomes folded and the nuclei sink in, and each is surrounded by a portion of cytoplasm to form a sporoblast. A single nuclear division then occurs, and the two nuclei elongate to form sporozoites each with a small cytoplasmic body.

9. Nuclear divisions are mitotic, but the longitudinal splitting of the chromosomes occurs without contraction. It is probable that ‘amitotic’ appearances are due to the incomplete incorporation of these long chromosomes at the telophase poles, and the multipolar divisions to the subsequent division of such ‘amitotic’ resting nuclei. Six chromosomes can be seen at the anaphase poles, but each is looped back so that it is V or J shaped. This chromosome number is characteristic of the divisions of both microgametogenesis and sporogony.

10. There is good evidence that, as in other Coccidia, reduction division occurs in the zygote, and that this is therefore the only diploid phase.