When, on 23 December 1949, Clifford Dobell died as the result of an unheralded cerebral haemorrhage, the world of biological science lost a remarkable figure and this Journal one of the most distinguished of its regular contributors. Dobell's name means much to protistologists all over the world, especially to students of the parasitic Protozoa, who recognize in him a great investigator of the animal microcosm. His contributions to the history of his science, culminating in the famous monograph on Leeu-wenhoek, reveal him also as a man of wide culture and endowed with a sense of the past such as is rare in these days.

1. It has previously been shown [by Dobell] that, in cultures of strain K 28c, Entamoeba histolytica could be maintained indefinitely and made to pass through all the stages of its life history.

2. It was also demonstrated that all non-encysting strains of E. histolytica could be induced to encyst in vitro by substituting their concomitant bacterial flora by that of strain K 28c.

3. In order to ascertain what part each constituent of the bacterial flora of K 28c played in the life of E. histolytica, a detailed analysis of this flora was carried out. It was found to comprise eight aerobic organisms (mostly of the B. coli group) and six anaerobes.

4. The properties of individual species and varieties of bacteria were studied by adding them to cultures of the amoebae or by hatching the cysts of E. histolytica in media previously seeded with the bacteria to be tested.

5. With the same end in view two methods were devised for producing simplified strains of E. histolytica associated with from one to four species of bacteria only. By treating the cysts with acriflavine, the mixed flora could be freed of the aerobic organisms, leaving only the spores of the anaerobes. The spore-bearing anaerobes, in their turn, could be eliminated by treatment of the mixture with gentian violet. By using these methods it was possible to produce cultures of ‘synthetic’ strains of E. histolytica accompanied by any desired combination of bacteria, whose properties it was desired to investigate.

6. The results of the earlier experiments suggested that the essential constituent of the flora of K 28c was B. coli, all varieties of which appeared to promote growth, induce encystation and excystation, and generally favoured the completion of the life-cycle of the amoebae in vitro, whereas the anaerobic bacteria present in the strain appeared to be inactive as regards encystation.

7. However, later experiments have demonstrated conclusively that, although the aerobic bacteria individually induced the cysts of E. histolytica to hatch and supported the growth of the amoebae indefinitely, only one species—the anaerobe N5—was capable of promoting encystation. As regards the aerobic bacteria, their chief role is to provide the anaerobic conditions necessary for the growth of the amoebae with N5 in culture.

1. Dobell's observations on the production of pure mixed strains of Entamoeba histolytica have been repeated and confirmed.

2. It has been demonstrated that the method devised by Rao did not sterilize the cysts of E. histolytica but merely killed all non-sporing organisms, while the spores of all spore-forming bacteria were unaffected.

1. After a general consideration of the host-parasite relations between E. histolytica and man, a case is made for the recognition of a commensal phase in the life history of this amoeba.

2. This view is supported by observations on the food habits of E. histolytica in chronic cases and carriers of human amoebiasis.

3. From these observations it is evident that from 30 to 100% of trophic amoebae in such cases have ingested bacteria derived from the contents of the large bowel.

1. The occurrence of cysts of the polecki type in an apparently healthy person in Pakistan is recorded.

2. The possible relationship of the polecki type cysts and the minuta form of E. histolytica is discussed.

A strain of Plasmodium gallinaceum has been treated for 16 months with chloroquine, under conditions which previously have produced strains resistant to proguanil, sulphonamides and pamaquin, but no change in reaction to the drug has occurred.

1. A four- to eight-fold increase in resistance to pamaquin has been developed in a strain of Plasmodium gallinaceum in chicks.

2. Pamaquin resistance conferred no resistance to proguanil, sulphadiazine, mepacrine, chloroquine or sontochin, but it conferred some resistance to pentaquine and to quinine.

3. An appreciable loss in resistance to pamaquin was observed in the pamaquin-resistant strain after it had been maintained in the absence of the drug, in a patent state of infection, for a period of 6 months.

4. No synergism was observed between pamaquin and quinine when these drugs were tested, in combined doses, upon active infections of P. gallinaceum.

In the skin of Rana temporaria from Czechoslovakia two unicellular parasites have been found: Dermocystidium ranae Guyénot & Naville and Dermosporidium granulosum n.sp.

Dermocystidium ranae. Two stages were found, one of which is new. An account is given of the morphology, development and occurrence of both stages, including details which have hitherto not been recorded.

Dermosporidium granulosum n.sp. This species is represented by cysts situated in the stratum spongiosum corii. They are divided by septa into small chambers containing groups of spherical spores with a central nucleus and with numerous small cytoplasmic inclusions. Within the cyst, the sporoblasts occupy the periphery, while the ripe spores are in the centre.

1. Areas in which theileriasis occurs are characterized by conditions in which the native cattle do not show clinical manifestations of the disease, but introduced cattle suffer from an epizootic manifesting itself seasonally with varied intensity.

2. The degree of virulence exhibited and the species of tick acting as vectors have only an indirect significance as an indication of species of the parasite.

3. The facts relating to the development of Theileria in the tissues of infected animals and relation of this to developmental stages in the circulating blood are still far from clear.

4. The development cycle of Theileria in the red cells of the circulating blood of sick animals is described, and proof given that this is characterized by the formation of anaplasmatic forms developing into ring-shaped forms in T. annulata and T. dispar, and probably in all forms except, possibly, T. parva.

5. It is very desirable from the point of view of world economy that a special commission to study theileriasis in the different areas in which it occurs should be established on an international basis.

The blood parasite described in this paper occurs in the diplopod Archiulus moreleti (the common garden milliped) which is too well known to warrant any description. The incidence of the infection fluctuates considerably, varying from almost 50% to about 1% in the same locality within the course of a few months. There is apparently no seasonal rhythm of incidence.

1. Permanent and temporary pastures were examined using a modification of Taylor's method.

2. The goodness of fit of Neyman's Contagious Distribution Type A when applied to larvae on pastures is discussed.

3. Examination of permanent pastures over a period of 3 years showed that the difference in time of maximum infestation was greater between fields in the same year than between years for the same field.

4. Counts made on pastures where disease had occurred showed reasonably close agreement with Taylor's estimate.

5. No larvae were detected on fields after ploughing and reseeding.

6. The number of larvae per lb. of herbage on reseeded pastures was low, but the growth of grass masked the fact that the total population was relatively high at the end of the season.

Pristotrema manteri n.g., n.sp. is described from the spiral valve of the shovel-nosed sturgeon, Scaphirhynchus platorhynchus (Rafinesque), in the Wabash River, Indiana, U.S.A.

A new genus, Pristicola, is erected for Dihemistephanus Little, 1930, nec Looss, 1901, with Pristicola sturionis (Little) as the type and only species.

The subfamily Deropristiinae Cable & Hunninen, 1942, is re-defined to receive the genera Pristotrema and Pristicola as well as the type genus, Deropristis.

The uncertain family position of the Deropristiinae is discussed without removing it from the Lepocreadiidae, although the independent status of that family may be questioned in the light of recent work.

1. Large numbers of Plagiorchis (M.) megalorchis n.nom. were found in the intestine of four turkey poults of a total of thirteen which had died on a farm in Radnorshire. Presumably the presence of the parasites was the cause of death.

2. The anatomy of the adult worm is described.

3. The first intermediate host of the parasite is Lymnaea pereger, and the second intermediate host any of the following species of insect larvae: Chironomus riparius Meigen, Culicoides stigma Meigen, Culicoides nubeculosus Meigen and Anatopynia (Psectrotanypus) varius Fabr.

4. The larval stages of the worm are described.

5. The life cycle has been demonstrated experimentally by the feeding of insect larvae containing encysted cercariae to turkey poults.

6. The turkey is probably not the normal host of Plagiorchis (M.) megalorchis. It is most likely that it occurs naturally in some species of wild bird, but this is not yet known.

The larval stage of Taenia taeniaeformis, namely, Cysticercus taeniae-taeniaeformis, has recently been described by the writer (1951), a detailed account being given of the musculature and of the excretory and nervous systems of the scolex and strobila. In addition, some abnormalities in structure were noted, chief of which was the spiral torsion observed in some specimens and which involved the musculature, excretory and nervous systems of the strobila but not the surface layers. A search was then made for some adult specimens in order to find whether the same abnormality could be seen and to ascertain what the effect of such a torsion would be on the genitalia in the mature and gravid regions. Several adult specimens, from the intestine of a cat, were given to the writer by Mr L. E. Hughes, veterinary investigation officer. Unfortunately, none of these specimens showed the identical spiral torsion found in the larva, but two of them had become knotted together, presumably at an early stage, and were considerably distorted in the regions involved in the knot. This distortion was again of a spiral nature but involved the entire proglottid and not only the internal structures as was found in the type of spiral torsion common in the larval stage of this species. The condition was not merely a turning over of the strobila but an abnormal spiral growth brought about by the continued constriction on the body where the two worms were twisted around one another. So here again, in the adult stage, spiral torsion is evident but from a different cause and involving the whole of the relevant segments from the surface layers to all the contained organs.

In June 1946, one male and one female helminth of the species Marshallagia marshalli (Ransom, 1907) were collected from one of two goats (Capra sibirica), at Manali, which had been slaughtered soon after their arrival from Spiti (Kangra district, Punjab, India). The abomasa, small intestines, lungs and livers of both the animals were available for examination. The lungs, livers and small intestines did not yield any helminths, but one male and one female of Marshallagia marshalli, were collected from the abomasum of one goat, and a single male specimen of Haemonchus contortus was collected from the abomasum of the other goat.

The description of one new species of Ascodipteron and another one of Nycteribosca is based on the material collected in Africa and Madagascar respectively by Mr H. Hoogstraal, of the United States Naval Medical Research Unit No. 3. These specimens represent a part of the collection which was sent to me for identification by Mr R. L. Wenzel of the Chicago Natural History Museum. In this paper I have also included the description of another new species of Ascodipteron of which two specimens were collected by Mr T. S. Jones in West Africa.

Three species of Listrophorid mites representing two genera, Alabidocarpus and Labidocarpus, are known from the European horse-shoe bat Rhinolophus ferroequinum, and one species of Alabidocarpus, A. nasicolus, has already been described (1938) from the closely related Natal horseshoe bat Rhinolophus geoffroyi zuluensis.

Of the fifteen valid species of mammalian blood-flukes so far known, six have been originally described from India. Montgomery (1906) described Schistosoma indicum, S. spindalis and Ornithobilharzia bomfordi (Montgomery, 1906) Price, 1929. Datta (1932) found that nasal granuloma of cattle is due to a new schistosome, which was subsequently obtained and described as Schistosoma nasalis by Rao (1933). Rao & Ayyar (1933) obtained a new schistosome from pigs and described it as S. suis. Mudaliar & Ramanujachari (1945) described S. nairi n.sp., from an elephant, which was transferred to the genus Ornithobilharzia by Bhalerao (1947). Another new species of blood-fluke has now been found in Indian buffaloes and cattle. While studying the larval trematode fauna of the local aquatic snails, large numbers of a new schistosome cercaria were obtained from nine out of three hundred specimens of Limnaea luteola examined during November 1950. When the cercariae were administered to two guinea-pigs, a buffalo-calf and a bull-calf, they developed into an interesting blood-fluke referable to the genus Ornithobilharzia Odhner, 1912. Subsequently, three out of thirteen buffaloes examined post-mortem were found to be naturally infected with the same parasite. The morphology of the adult and of its cercaria is briefly described in this paper.

The identification of Ixodes frontalis Panzer, 1795, from earlier descriptions presented great difficulty, more particularly as the species is rare. There are two specimens in the British Museum (Natural History), and the description by Schulze (1933) is from a single specimen in the Sofia Museum. The rarity of the species led Schulze to write that ‘Die Art ist in Deutschland seit den Zeiten Panzers nicht mehr wiedergefunden worden’. Senevet (1937), who considers I. frontalis synonymous with I. brunneus Koch, 1844, wrote that the species occurred in St Genies-de-Malgoires in France, but this information was taken from Nuttall, Warburton, Cooper & Robinson (1911).

During the course of an investigation into the host-relationship of Ixodes hexagonus Leach a large number of birds was examined for its occurrence. These all proved negative for this species, but I. passericola Sch. was present on one robin out of 220 examined, on one starling out of eleven, on seventeen great tits out of 163, on twenty blue tits out of 540, and on four nuthatches out of fifty. A detailed report on this aspect is given later.