Our knowledge of the Indian Rhynchobdellid leeches is still in its infancy, and the little that we have, we owe to the researches of Harding, Kaburaki, and Moore. After the publication of the Hirudinea volume by Harding & Moore (1927) in the Fauna of British India Series, Bhatia (1930a, b, 1934, 1939), Chelladurai (1934) and Raj (1951, 1954a, b) have contributed to the systematics of this group. The present work has been undertaken with a view to advancing further our knowledge of Indian Rhynchobdellid leeches. In this work, the neurosomic theory of somite limits launched independently by Castle (1900) and Moore (1900) has been followed in counting the annular composition of somites. This paper, the first of the series, deals with the description of four Glossiphonid leeches, of which three are new to science, while the fourth one is of zoogeographical importance.

An account is given of the occurrence of Parabothrium gadi-pollachii and Abothrium gadi in some members of the Gadidae caught in the north-eastern Atlantic.

The external features, musculature, excretory, nervous and genital systems of the two species are described in detail.

The adults of both species are characterized by the absence of a typical pseudophyllidean scolex and possess interesting modes of attachment to the intestine and caeca of the host. The variation found in individuals of A. gadi from the cod and haddock is discussed.

The last twenty-five years have witnessed an increasing output of significant work in this country on the trematode parasites of a number of wild birds, including aquatic species. These studies, which are mostly faunistic, and can be said to have commenced in 1926, when Bhalerao (1926) described from Burma (then a province of India) the flukes of the house crow, deal primarily with a large number of representative species of nearly twenty families of Digenea. Of these families, species assignable to the Clinostomidae Lühe, 1901, the Cyathocotylidae Poche, 1926, the Cyclocoelidae Kossack, 1911, the Diplostomidae Poirier, 1886, the Echinostomatidae Poche, 1926, the Notocotylidae Lühe, 1909, the Opisthorchiidae Braun, 1901, and the Strigeidae Railliet, 1919, were encountered in a survey conducted to assess the nature of helminthic infections in wild aquatic birds of the Mathura area.

When third-stage trichostrongyle larvae exsheathed, they released an exsheathing fluid which eroded the sheath at the anterior end. This led to the formation of a refractile ring and ultimately to the fracture of the sheath which enabled the larva to escape.

Exsheathment was induced by ovine rumen fluid. The exsheathing activity of rumen fluid was impaired by centrifuging, filtering, boiling and aeration, but activity could be restored by the addition of reducing agent. The activity in vitro of either fresh rumen fluid or freeze-dried rumen fluid, after addition of a reducing agent, was comparable with that obtained in vivo.

After stimulation, the process of exsheathment continued in the absence of rumen fluid. The ability of rumen fluid to stimulate larvae was dependent upon temperature, hydrogen-ion concentration and oxidation-reduction potential.

Exsheathing fluid was present in larvae both before and after exsheathment. Larvae which had been stimulated to exsheath released exsheathing fluid for a brief interval and further release could be obtained only after the stimuli had been temporarily withdrawn.

The mechanisms for reception of the stimulus to exsheath and for storing and releasing exsheathing fluid were located in a region between the base of the oesophagus and the excretory pore. The fluid was probably released from the excretory pore.

Exsheathing fluid from one species was not necessarily as active against sheaths from other species as against its own. The activity of exsheathing fluid was dependent upon the presence of a heat-stable cofactor of low molecular weight. Activity of the dialysed fluid could be restored by addition of MnCl2 or MgCl2. Values of Q10 for the action of the fluid on the sheath lay between 1·3 and 1·9. Activity was inhibited by Hg2+, Fe3+ and iodoacetic acid.

1. Mehlis's gland secretion in trematodes and pseudophyllidean cestodes may be a lecithin-like phospholipid.

2. After enzymic degradation of the lecithin into lysolecithin the release of egg-shell precursors from the vitelline cells is effected.

3. Soon after the completion of the egg-shell the lysolecithin may be reconverted into lecithin in vitelline cells of Penetrocephalus ganapatii, thus accounting for the periodic acid-Schiff positive reaction.

1. Herpetomonas ludwigi was found in 5–6% of larvae of Tipula paludosa in two out of three populations examined.

2. The developmental cycle is confined to the enteric caeca of the host. From a study of smears and sections of these organs it was concluded that the life cycle was composed of the following stages:

(a) A long-flagellated leptomonad stage which is short-lived and probably represents the form in which the flagellate enters the caeca from the mid-gut lumen; (b) a haptomonad or attached form in which the flagellum is short or absent: this probably represents the growth phase of the organism; (c) a crithidial phase which arises by a series of divisions from the haptomonad; (d) a small trypaniform stage which breaks free and lives in the lumen of the caecum; (e) a precystic flagellate; and (f) a small, thick-walled cyst.

3. This species is characterized by its restriction to the enteric caeca and the short duration of free swimming as opposed to attached stages in the life history. This second feature is a corollary of the first. The periodic contraction of the enteric caeca makes attachment obligatory throughout the growth and division stages. These contractions also serve to void cysts into the mid-gut whence they leave the larva with its dejecta to infect other larvae.

1. The dorsal plate which probably represents a rudimentary scutum in some Argasid larvae is discussed and described.

2. The respiratory system of the larvae of some species of Argas and Ornithodorus is described.

3. The systematic position of the lahorensis group of the genus Ornithodorus is discussed and the use of the name Alveonasus with an emended diagnosis for this group is suggested.

4. Ornithodorus procaviae n.sp. is described. Two other probably new species are described provisionally, but not named.

5. New records for other species of Argasidae in Israel are given.

1. A spring-rise in faecal strongyloid egg count is described in sheep housed under conditions designed to prevent reinfestation. Large rises were observed in the majority of 3-year-old breeding ewes and primiparous ewe-hoggs, and occasional small rises occurred in nulliparous ewe-hoggs and wether-hoggs.

2. Falls were observed in the packed red-cell volumes of ewes during the period of spring-rise and a close inverse correlation was found between packed-cell volumes and transformed worm egg counts. No evidence was obtained to attribute the falls in packed-cell volume to factors other than worm burden.

3. The fall in packed-cell volume was partially alleviated by feeding of one type of perennial rye-grass, but no direct effect of feeding on the worm-egg output was found.

4. Theories of spring-rise are discussed and the conclusion reached that latent overwintering larvae must play a major part generally in the phenomenon.

1. Observations have been made on the life cycles of Cercaria paracauda, Iles, G. tetraglandis, Iles, and C. Apatemon gracilis minor, Yamaguti. The development of the tetracotyle metacercaria of C. tetraglandis has been followed and also that of the metacercaria and adult of A. g. minor. The pathology and distribution of the metacercariae of the last two species within the leech, Erpobdella testacea (Sav.) has been studied.

2. It was noted that development of the metacercariae within the same host and resulting from the same infection was not simultaneous and that it was improbable that a 100 % encystment of the metacercariae would occur. Temperature was found to have a marked effect on the length of time required for encystment.

3. Data are given on the infectivity and excystation of the metacercariae of A. g. minor and on the biology and morphology of the adult of this subspecies.

4. Stress is placed on the importance, in the systematics of the digenetic trematodes, of considering both the morphological and biological characters of the adult and those of the related larval stages.

Rabbit serum containing cytoplasm-modifying antibodies was fractionated by alcohol precipitation at low temperature and controlled ionic strength and pH. The highest cytoplasm-modifying antibody titres were observed in fractions that contained γ-globulin.

The nematodes described below were collected by M. L. Emanuel from two specimens of the pouched mouse, at Innisfail, North Queensland. They were very kindly sent to the author by Dr M. J. Mackerras of the Queensland Institute of Medical Research. Both species of parasite were present in both host animals. Trichostrongyles have not previously been described from phascogales but a metastrongyle, two spirurids, and a rictulariid, are listed by Dr Mackerras in her check-list of parasites of Australian mammals (Mackerras, 1958). To these may now be added the present records, the details of which are as follows: Phascogale flavipes (Waterhouse, 1838). Innisfail, Queensland. Nicollina phascogale sp.nov., Tetrabothriostrongylus mackerrasae gen.nov., sp.nov.

1. Gametocytes of Plasmodium gallinaceum emerged from the erythrocytes and the male gametocytes exflagellated normally in vitro, in normal or inactivated horse serum, or in rabbit plasma.

2. Gametocytes, washed and suspended in normal horse serum, completed their sexual development and produced oocysts in mosquitoes.

3. Hyperimmune chick plasma, as compared with normal chick plasma, did not significantly affect the time of onset or the frequency of exflagellation.

4. In a solution, isotonic to bird blood and adjusted to approximately pH 8, containing NaCl, KC1, CaCl2, Na2HPO4, MgSO4, NaHCO3 and Tris buffer, the in vitro development of the gametocytes was normal, and the numbers developing were comparable to those in horse serum, or in plasma or serum from the normal host. The development of the gametocytes was inhibited by the omission of Na or HCO3 ions, but the omission of Mg, K, Ca, SO4 or HPO4 ions had no effect.

5. Further experiments showed that the gametocytes emerged from the corpuscles and the males exflagellated normally in a solution containing only Na, C1 and HCO3 ions. Other combinations of ions were tested, but although gametocytes emerged from the corpuscles in some of these solutions, exflagellation either did not take place or did so infrequently, and the gametes produced were feeble in their movements. Within the range of inorganic salts tested, Na, HCO3 and C1 ions constituted the minimal requirement for the normal in vitro development of the male gametocytes.

The infectivity and invasiveness of a single strain of Entamoeba histolytica to young rats has been studied over a period of 12 years. The virulence was slowly lost over a period of months or years of cultivation in vitro. After four to six liver passages, virulence was again established and again declined in culture. This was repeated on three occasions. Each time the strain lost virulence, the capacity to invade the mucosa was lost before the amoebae became non-infective to young rats. The duration of experimentally acquired virulence was progressively reduced after each succeeding series of liver passages.

1. Four stages in the development of Choanotaenia crassiscolex are described with the help of five text figures and one plate.

2. The functional anatomy of the cysticercoid is given with the help of diagrams.

3. The identification is based on comparisons with material at the British Museum of Natural History, South Kensington, London, and comparison is made with earlier records in Table 1.

4. The unusual cyclophyllidean scolex is discussed and tentative suggestions and queries concerning the general form of the early cysticercoid are put forward.

5. An attempt is made to determine more precisely than has hitherto been done for cysticercoids, the relationship of parasite and host.

The development of Carmyerius exoporus Maplestone in the snail Anisus nata-lensis Krauss is described with the emphasis laid on the redial and cercarial productivity of the rediae of the first and subsequent generations.

The miracidium gives rise to one sporocyst. From 25 to 32 germinal cells present in the miracidium, only six to eleven develop into embryo balls in the sporocyst and, of these, only three to nine develop into rediae of the first generation.

The redia of the first generation gives birth to daughter rediae and cercariae. No alternation in the development of redial and cercarial embryos was noted in the rediae of C. exoporus and a small number of redial embryos was observed to develop alongside the more numerous cercarial embryos throughout the life of the first generation rediae.

The rediae of the second and subsequent generations also give birth to daughter rediae and cercariae.

The cercariae leave their parent redia when they are still immature and continue the development in the snail tissue.

1. The tracheal systems of first, second and third instar larvae of Gasterophilus intestinalis are described.

2. The homologies of the conical tracheae of the tracheal organ are demonstrated and explain the apparent disappearance of a complete tracheal metamere.

3. Anomalies in the tracheal system of the anterior segments of Gasterophilus led to an investigation of the tracheal systems of Drosophila, Eristalis, Calliphora, Scatopse and Aëdes.

4. The anterior tracheal system of larval Diptera has been re-interpreted; that of the Cyclorrhapha can be derived from that of the Nematocera without the formation of new tracheae other than a large trachea from the lateral longitudinal trunk to the antero-lateral musculature.

1. It has been observed that the larvae of four species of chironomid midges invade and destroy the contents of the egg masses of Bulinus (Physopsis) globosus in Amani lake, Tanganyika.

2. There was no indication that this type of predation exercised any restraint on the density of adult snails.

Lipid material occurs in the oocysts of Plasmodium in the form of small Sudano-phil granules, which appear to increase in size with the growth of the parasite. A diffuse Sudanophil material also appears at a later stage.

Phospholipid occurs at a certain stage of the oocyst, but later disappears altogether. It appears more quickly in some oocysts than in the others, found in the same infected gut.

The pre-erythrocytic schizonts of P. cynomolgi are found to contain abundant lipid material.

The erythrocytic stages of Plasmodium and Hepatocystis cannot be stained with the Sudan dyes, but the gametocytes of Hepatozoon infecting the blood corpuscles of the vertebrate hosts are found to contain abundant Sudanophil material.

Sudanophil material can be detected in the unsporulated oocysts of Eimeria stiedae, but not in the sporulated ones.

Glycogen proved to be absent in the malaria parasites (Plasmodium and Hepatocystis) by applying cytochemical methods; while in the piroplasms (Theileria and Babesia), and in Hepatozoon glycogen could be demonstrated by using the same methods. A strong positive reaction for polysaccharides was obtained in the residual masses of Hepatozoon sciuri, and H. balfouri; while a negative reaction was obtained in the residual mass of Plasmodium. A positive reaction for polysaccharides was obtained in the following structures: the wall of the oocysts of Plasmodium, the gametocyte capsules of Hepatozoon sciuri and Hepatozoon sp., the sporoblast capsule of H. sciuri, and the polar areas of the gametocyte of H. balfouri.

1. Trypanosomes were found in the blood of thirty-five of seventy-two fish of five genera (chiefly Tilapia spp.) from Lakes Victoria and George, Uganda.

2. The trypanosomes, which were never numerous in the blood, showed two morphological forms—small (22–44μ. long) and large (45–65μ). No significant differences were observed between the trypanosomes from the different species of fish, and all the trypanosomes seen are provisionally identified as Trypanosoma mukasai Hoare, 1932.

3. Crithidia were found in the gut of a glossosiphoniid leech which had been removed from a fish; although suggestive, this cannot be taken as conclusive evidence that leeches of this family are vectors of T. mukasai.

4. The taxonomy of the trypanosomes of African fresh-water fish is reviewed, and it is concluded that only the following species should be regarded as valid at present: T. toddi Bouet, 1909, T. mukasai Hoare, 1932, and T. tobeyi Dias, 1952.

5. Dactylosoma mariae Hoare, 1930, was found in the blood of thirty-six of the seventy-two fish examined. Merozoites, schizonts and gametocytes of this small unpigmented parasite were observed within erythrocytes. No developmental stages were found in certain viscera of two infected fish.