By employing a combination of sub-stage heating and supra-vital staining with eosin or neutral red it was found that viable and non-viable hydatid scolices could be distinguished microscopically. Using this technique a study of the effect of heat in vitro on hydatid scolices has shown that death resulted from exposures at 50° C. for 70 min. and at 55° C. for 30 min.

Experiments on the effect of boiling in destroying the contents of fertile cysts embedded in sheep liver showed that when offal was added directly to boiling water destruction of scolices was complete after 40 min. boiling. When the infected liver was placed in cold water brought to the boil, scolex death was assured only after 30 min. subsequent boiling.

Ultra-violet radiations of 2537 A. did not kill scolices under the conditions adopted. Although this wave-length would apparently be ineffective as a scolicicidal agent in surgery of the human hydatid cyst, irradiation of hydatid fluid containing scolices might offer a simple method for initial sterilization of scolex culture media.

The author wishes to acknowledge many helpful suggestions and loan of the Hanovia lamp by Dr G. M. Richardson of the Virus and Immunology Research Department, Otago Medical School.

The material described in the present paper was collected by Dr Rašín in 1935. It consisted of an infected ovary of Leuciscus cephalus L. from the Svitava river near Brno, and an ovary of Esox lucius from Ríčka in the vicinity of Vranovice near Brno, C.S.R. The ovaries were fixed partly with formol-Zenker solution, and partly with Gilson's fixative. The infected roes could be distinguished easily from the healthy ones by their white colour. Histological examination showed that they were infected with Microsporidia. As the material had been fixed, no polar filaments could be observed. Sections, 4μ in thickness, were stained with Heidenhain's iron haematoxylin, which once more proved to be a stain which gave the greatest contrast in preparations of Microsporidia. In addition, sections were stained with Mallory and Mann's stains, and were also subjected to Feulgen's nucleal reaction.

On the whole published data on the host relationships of Ixodes ricinus L. in Britain are rather inadequate, but the following points emerge:

The tick (stages unspecified) has been found on twenty-three mammal, twenty-one bird and one reptile species. These include both wild and domestic animals. There are no records of non-hosts. The host list is incomplete. Its length and variety suggest, however, that the tick will feed on practically any mammal or bird it may meet.

Tick stages found on fifteen mammal, twenty-one bird and one reptile species have been recorded. For a number of reasons (see text) ‘recorded’ absence of any tick stage from an animal is not necessarily reliable. This, together with the incompleteness of the host list, detracts a little from the assertion of several authors, namely, that in general larvae and nymphs occur on both mammals and birds, but adult ticks on mammals only.

No precise host-potentials for any wild species relative to sheep (or other important farm stock) have been published in Britain. But, in one area, Scottish mountain hare, red deer and roe deer have been slaughtered on a large scale because of their alleged importance as hosts. Very inadequate data from two authors seem to suggest that as normally stocked populations (a) grouse are negligible compared with sheep as hosts to female ticks, and (b) mountain hare and red deer may play quite an important part in maintaining female ticks. Suggestion (b) at least should not be taken seriously until comprehensively investigated.

One author shows that an ‘appreciable’ tick population was maintained on a hill grazing by a reduced wild fauna in the absence of sheep.

Another author shows that the tick population of a grazing was considerably reduced by acaricidal treatment of sheep, together with almost complete extermination of a section of the wild fauna. Unfortunately, the two factors cannot be disentangled.

We would like to thank Mr Charles Elton, Director, Bureau of Animal Population, Oxford, and Dr J. MacLeod of the Cooper Technical Bureau, Berkhamsted, for criticism of the MS.; Mr F. Wallace for information on red deer stocking; and Dr V. B. Wigglesworth, F.R.S.,. Director, Agricultural Research Council Unit of Insect Physiology, Cambridge, within whose organization the work was done.

Although three other Ixodes species were found, Ixodes ricinus L., when it occurs, is by far the most important tick parasite of wild and domestic animals on hill and moorland grazings in northern England. In the following, ‘tick’ or ‘ticks’ refer to I. ricinus.

The previous list of British mammal hosts, wild and domestic, to the tick (any stage) is largely confirmed, and increased approximately from twenty-three to twenty-nine species; and birds, similarly, from twenty-one to thirty-nine species. The preponderance of small mammals and birds among the twenty-four new-recorded host species confirms the impression that previous workers tended to confine their attentions to the larger animals. The host list is still incomplete, and the suggestion that the tick will parasitize any bird or mammal it may meet is strongly reinforced.

No host occurs below the reptile level among vertebrates; and among British reptiles, only the common lizard is a host—rarely. There appear to be no hosts among invertebrates.

All the farm and domestic mammals from horse down to cat are hosts to female ticks, but poultry have never been recorded—probably because they do not much frequent the tick-infested pastures.

Only the larger wild mammals and birds are hosts to female ticks. In northern England these include eight mammals and three birds. For Britain as a whole two other mammals are known, while a further four mammals and one bird are likely hosts.

With or without the inclusion of domestic animals, proportionately more mammal than bird species are hosts to female ticks. This is because there are more mammal than bird species large enough to be hosts.

All the recorded British hosts, except shrew and possibly mole, are hosts in some degree to nymphs, and all, without exception, are hosts to larvae.

A certain amount of self-deticking is practised by birds, and very probably by some of the smaller mammals. Birds never have ticks attached within beak-reach.

In the course of recent work on the pathogenicity of Trypanosoma vivax in bovines, cases have occurred at the Veterinary Laboratory, Entebbe, when it has been difficult to diagnose the species of trypanosome occurring in the blood. This difficulty arose because many of the trypanosomes were too small to be typical T. vivax and the possible occurrence of T. uniforme had to be considered, and also because many abnormal degenerate forms appeared at irregular intervals. A more detailed study of the trypanosomes present in the infection was therefore undertaken and, although in many aspects this work is still incomplete, the course of the infection in goats and sheep has been sufficiently interesting to merit this preliminary report.

Four specimens of this parasite were collected from the gills of about two dozen Dussumieria acuta, a fish which is of market value in Madras. Of the four specimens, two were female and two were male; no two were found in the same fish. Both the males were 1·5 mm. long, while the two females measured 2·6 and 2·5 mm. respectively.

Joyeux & Baer, in 1935, recognized a new genus when they described Pseudoporrorchis houdemeri, a new species of Acanthocephala taken from the intestine of Centropus sinensis intermedius at Tonkin, Indo-China. They reviewed the literature and assigned four additional species to this genus as follows: Echinorhynchus rotundatus von Linstow, 1897; E. centropi Porta, 1910; E. bulbocaudatus Southwell & Macfie, 1925; and E. centropusi Tubangui, 1933. These same authors presented a tabular comparison of the five species, based upon all of the usual morphological details utilized in formulating specific descriptions. Morphologically the five species show close conformity in all essential features. In their host relations they are equally uniform in that each species utilizes some species of the avian genus Centropus as its definitive host. In the present paper a sixth species of this genus is described in which the same adherence to general morphological pattern is observed, although the definitive hosts are mammals instead of the customary bird hosts.

In recent papers I have given, in relatively compact form, lists of the genera and species of metastrongylid lungworms; these publications are in turn summarized in a paper which follows (Dougherty, 1948). However, the trichostrongylid lungworms, constituting the subfamily Skrjabingylinae Skriabin, 1933, have not been completely treated, although in a recent work (Dougherty, 1945), in which certain lungworms were formally transferred from the Metastrongylidae to the Trichostrongylidae, the Skrjabingylin genera were listed without critical appraisal, and in the same paper the genus Crenosoma Molin, 1861, was reviewed in detail; subsequently the genus Dictyocaulus Railliet & Henry, 1907, has also been reviewed (by Dougherty, 1946).

1. History of the classification of the family Metastrongylidae is briefly reviewed.

2. The probable origin of the family is discussed. It is believed that the metastrongylids arose, in common with the family Strongylidae, from a primitive group of eustomatous, cloacinin-like, gastro-intestinal strongylines that were symbiotic with an ancestral mammalian group, possibly the pantotheres. One group of these symbiotes established itself in the mammalian respiratory tract and originated the metastrongylid line.

3. The family Trichostrongylidae is regarded as of common origin with the family Ancylostomatidae from eustomatous ancestors. Thus meiostomy in the metastrongylids and trichostrongylids is convergent.

4. The Metastrongylidae consist of three main lines, each characteristic of a placentate order: the Filaroidinae in the Carnivora, the Pseudaliinae in the Cetacea, and the Protostrongylinae in the Artiodactyla. These lines probably have evolved from a common ancestor, symbiotic with a host at the base of the carnivore-cetacean-ariodactyl radiation. Certain forms have become secondarily adapted to symbiosis with members of other placentate orders.

5. Morphological and biological evidence is given for each of the foregoing phylogenetic conclusions.

6. Metastrongylus Molin, 1861, is regarded as a relict genus. With it, in a subfamily Metastrongy-linae, is placed the genus Heterostrongylus Travassos, 1925.

7. Heterostrongylus is represented by a single known species, H. heterostrongylus Travassos, 1925, from an opossum (order Marsupialia). Morphologically it is primitive with cloacinin-like cephalic features. In view of the phylogenetic status of its host it may well represent an ancestral type that has evolved along with the Marsupialia from a common ancestry with the other metastrongylids, probably in the panthotheres. As yet unknown lungworms of marsupials may shed light on this interesting point.

8. Diagnoses are given for the family Metastrongylidae and its subfamilies; the twenty-two component genera are listed under the latter. New synonymies are made: Neometastrongylus Kreis, 1944, a synonym of Neostrongylus Gebauer, 1932; Neometastrongylus buechii Kreis, 1944, of Neostrongylus linearis (Marotel, 1913) Gebauer, 1932; and Otophocaenurus Skriabin, 1942, of Pharurus Leuckart, 1848. Otophocaenurus oserskoi Skriabin, 1942, becomes Pharurus oserskaiaae (Skriabin, 1942, n.emend.) n.comb.; Metathelazia massino becomes M. massinoi (Davtian in Skriabin, 1933, n.emend.) Dougherty, 1943.

It is a common observation that in individual Ixodes ricinus L. ticks, size variations occur; such variation is reflected in the records of early workers (Wheler, 1899; Neumann, 1899: quoted by Nuttall, Warburton, Cooper & Robinson, 1911). The present paper attempts to examine the true specific importance of size variation by basing the study on measurements of the relatively inelastic scuta after the principle of using head capsule measurements for insectan larval instars.

During the course of work carried out in 1941 at the Plant Diseases Division, Auckland, N.Z., on a mixture of X strains in Red Dakota potatoes, it was found that among the twenty solanaceous species tested in host range studies, Cyphomandra betacea gave an anomalous reaction.

1. Compared with the mammalian intestine, uterus and blood serum, the corresponding organs and perienteric fluid of Ascaris lumbricoides were found to have a high phosphorus content. The muscle of the parasite, however, contained little more than half the phosphorus found in the mammalian muscle.

2. A. lumbricoides took up inorganic ortho-phosphate largely or exclusively through the alimentary tract. Small amounts were taken up by the cuticle and the lateral line system, but did not appear to pass on to other tissues.

3. Nippostrongylus muris in the intestine of the rat took up radioactive phosphorus which had been injected into the host intramuscularly. When the host was dosed per os the radioactivity appeared in the parasites at a lower concentration than in the host's small intestine.

4. Ascaridia galli failed to show any radio-activity when host birds were injected intravenously with inorganic orthophosphate containing P32. A sudden rise and fall in the radioactivity of the parasites were found when host birds were dosed per os.

5. It is suggested that nematode parasites have a high demand for phosphate which they take up largely per os. Ascaridia galli feeds rapidly, but with poor phosphate absorption, on host gut contents. Nippostrongylus muris feeds on host tissues. It is suggested that the different feeding habits of N. muris and Ascaridia galli may have some relation to the efficacy of anthelmintics against these parasites.

The authors are indebted to Dr M. Kamen and Dr E. Reinhard of Washington University, St Louis, for a gift of radioactive phosphorus. Thanks are also due to Mr E. Parrish and Mr L. Turk of the McMaster Laboratory for their capable assistance.

Three species of lung nematodes have been found in Felidae in Palestine: Aelurostrongylus abstrusus, Troglostrongylus brevior n.sp. and Anafilaroides rostratus n.g., n.sp. The life histories of all these species have been studied. Their larvae develop in terrestrial molluscs. Some new observations on the factors influencing the development of the larvae of Aelurostrongylus abstrusus are described. The whole developmental cycle of Troglostrongylus brevior has been experimentally reproduced. Initial stages of the development of the larva of Anafilaroides rostratus in molluscs have been observed. The taxonomic position of the genera Aelurostrongylus and Troglostrongylus is discussed and their protostrongyline character is demonstrated.

1. The nomenclature and synonymy of the Leishmania of man and of the dog is reviewed.

2. Many of the older names have been discarded and medical writers now recognize only two, or at the most three, species of Leishmania of man and dogs.

3. These species are indistinguishable morphologically. Attempts to differentiate them by the techniques of bacteriology have given conflicting results and there is no general agreement that they can be so differentiated.

4. It has been suggested that separation of species of Leishmania is not justified under the present rules of systematics and that all forms of human and canine leishmaniasis must be regarded as the result of infection by a single species of parasite.

5. This suggestion is not entirely acceptable in view of contributions to the subject by medical workers who have studied the results of infection in the human subject intensively and continuously for half a century.

6. Evidence is produced that the different types of human leishmaniasis recognized clinically can be correlated with biological differences in the causal parasites.

7. In other organisms which have been intensively studied the existence of groups which differ from each other in biological characters only is widely recognized in modern systematics, but there is no general agreement about nomenclature for the definition of such groups.

8. Reasons, not inconsistent with modern studies in systematics, are given for the recognition of at least three groups in the Leishmania of man, corresponding with the L. donovani, L. tropica and L. brasiliensis of medical text-books. Definition of the taxonomic status of such groups will depend on the further progress of systematics.

Observations on the larvae of sheep trichostrongyles on hill pastures showed:

1. A reduction in larval populations occurred when the ‘moving-flock’ type management was used. The large proportion of eggs passed in faeces is deposited on a part of the pasture where little or no grazing occurs.

2. Local concentrations of larvae occurred on the grazed portions of a pasture when grazing was uneven. Thus, the apparent low rate of stocking on hill pastures does not give a true picture of the potential dangers of parasitic disease. Estimates of pasture contamination by Taylor's method of sampling were deceptively low.

3. The number of larvae on grass blades was lowest when the grass was wet with dew. Sampling of pastures between 12 noon and 5 p.m g.m.t. gave maximal and most constant estimates.

4. There was an increase in the number of larvae on a pasture during the warmer months of the year. While low temperatures prevent or delay hatching, the increase in population was not entirely due to the increased rate of development when temperature was high. The increase in numbers was partly due to an increase in the number of adult worms in the sheep hosts.

5. Removal of sheep for 3 weeks reduced the number of larvae on a pasture. This reduction was not apparent, however, until after the first 12 days. After 3 weeks the pasture population was reduced by 55 %, while after 4 weeks (i.e. 7 days after the return of the sheep) the reduction was 90%. Two weeks later there was a small increase in the larval population, but this was again reduced with the onset of colder conditions.

1. The rate of penetration of some representative drugs into Ascaris lumbricoides var. suis has been measured.

2. The series of 4-n-alkyl resorcinols shows a typical homologous series effect.

3. l-Nicotine penetrates relatively slowly.

4. Its rate of penetration is greatly influenced by the extent of dissociation of its methyl pyrrolidine basic group.

5. The rate of penetration of nicotine is greatly accelerated in the presence of some surface active substances.

6. Chloroform is the most rapidly penetrating substance studied, and its penetration is not significantly influenced by the presence of proteins, carbohydrates and fats and their products of digestion.

7. An analysis of the experimental results shows that the outermost layer of the cuticle of Ascaris is probably the main barrier to penetration. It behaves as if it were a thin; homogeneous layer of lipoid.

8. The significance of these results in the study of anthelmintics is assessed.

1. The morphology and life history of a gregarine Lankesteria culicis (Ross), as it lives in the gut of Aëdes (Finlaya) geniculatus (Olivier), are described. The earlier stages are intra-epithelial in the fore and anterior mid-gut of the larvae. After a period of growth the trophozoites are liberated into the gut lumen where they attach themselves to the epithelium by a well-developed epimerite which functions as a sucker. Cyst formation and further stages in sporogony take place in the malpighian tubules when the larvae develop into the pupae. In the adult mosquito only ripe sporocysts are found, packed in the malpighian tubules and scattered in the hind-gut. The spores escape through the alimentary canal.

2. The systematic position of Lankesteria is reviewed. In view of its true dicystid nature, combining both acephaline and cephaline features, it is suggested that its proper systematic position would be in the dicystid family Lecudinidae Kamm emend. Reichenow, 1929, which includes all forms intermediate in position between the monocystids and the true tricystids.

1. The distribution of Cimex hemipterus and C. lectularius in the Sudan is described. Leptocimex boueti has been found in two localities.

2. Reasons for the distribution of the two species of bed-bug are discussed, and it is considered likely that facilities for dispersal and atmospheric humidity may have been the most important factors.

While investigating the nutrition of parasitic helminthes it became possible to estimate the amounts of several members of the vitamin B complex in the parasites. Information on this point was required in order to obtain some idea of the composition of a satisfactory in vitro diet.

1. The r.q. of whole Neoaplectana glaseri rose from 0·56 to 1·10 when glucose was added to the medium. The Qo2 was only slightly affected. Respiration of other nematode parasites was largely unaffected by exogenous glucose. Pyruvate had little or no effect.

2. Inorganic phosphate increased when Ascaris lumbricoides muscle brei was incubated. In the presence of fluoride, or when aqueous extracts were used, easily and difficultly hydrolysable phosphate was formed. Phosphatase activity was dominant even in aqueous extracts of A. lumbricoides intestinal tissues and fluoride inhibited Po formation only slightly. Ptot., and PresIdual fell markedly in whole A. lumbricoides which had been incubated anaerobically. Under aerobic conditions Po fell slightly, but the other components rose considerably. Phosphorylative activity of A. lumbricoides ovary was greater than in the muscle. Phosphorus compounds in perienteric fluid did not change during incubation.

3. The breakdown of glycogen and the formation of glucose in aqueous extracts of Ascaridia galli was inhibited by fluoride and phloridzin. Polysaccharide was synthesized in fluoride-poisoned preparations when glucose 1-phosphate was added. Polysaccharide formation in Ascaris lumbricoides fluoridepoisoned muscle preparations was demonstrated without the addition of Cori ester.

4. Fructose 1:6-diphosphate added to aqueous extracts of Ascaridia galli and Nematodirus spp. was rapidly metabolized at pH 6·5. At pH 7·2 the fructose content increased.

5. In aqueous extracts of Nematodirus or Ascaridia brei which had been autolysed for short periods, 55–60% of the glycogen utilized appeared as glucose. Only small amounts of lactate were formed. Aqueous extracts of Nematodirus and Ascaridia brei which had been autolysed for long periods formed glucose in excess of the glycogen disappearing. When perienteric fluid, which contained amylase, was removed from A. galli before autolysis, the amount of glucose formed was very much reduced. It is suggested that the excess glucose was formed from dextrins which were not estimated as glycogen and which were hydrolysed by perienteric fluid amylase during incubation.

Lactate decreased during the incubation of extracts prepared from brei which had been autolysed for long periods.

6. Bicarbonate decreased during the anaerobic incubation of aqueous extracts of Nematodirus spp. and Ascaridia galli which were buffered with CO2-bicarbonate. The decrease in bicarbonate was in excess of the CO2 expelled from the medium by acid formation.

7. The acid-soluble phosphorus compounds of the different tissues of Ascaris lumbricoides were examined. Compounds similar to a.t.p. were found in the intestine, ovary, muscle and possibly also in the perienteric fluid. The acid-unstable phosphorus compounds did not appear to be either creatine- or arginine-phosphate. Compounds similar to Embden ester were found in the ovary and muscle. The occurrence of the phosphate compounds found in the parasite is compared with figures given for other organisms.

8. It is concluded that carbohydrate fermentation as far as lactate in nematode parasites was similar to that found in yeast and mammalian muscle. Energy was transferred by means of high-energy phosphate bonds.

9. Phospholipids, which were found in considerable amounts in the tissues of A. lumbricoides, were estimated as lecithin, sphingomyelin and serine- and ethanolamine-containing phospholipids. The amounts of the phospholipids found in the parasite tissues are compared with figures given for other organisms.

The authors are deeply indebted to Prof. D. Keilin and Dr T. Mann of the Molteno Institute, Cambridge, for their advice and critical reading of the manuscript. Thanks are also due to Dr E. F. Gale and Dr E. Friedemann for advice on analytical procedures.