A generic diagnosis is given together with notes on infraspecific variation of known species in the subgenera Pterygosoma Peters, 1849, and Gerrhosaurobia Lawrence, 1958, and first descriptions of the following hitherto unrecorded stages. Males of P. transvaalensis, P. triangulare, P. hirsti hirsti, P. melanum melanum, P. melanum longipalpe, P. agamae aculeatum and P. persicum; nymphae of P. transvaalense, P. neumanni, P. agamae agamae and P. persicum; larvae of P. neumanni and P. agamae agamae. The following species are here considered to be subspecies: P. hirsti bedfordi Lawrence, 1936, P. melanum longipalpe Lawrence, 1936, P. agamae aculeatum Lawrence, 1936. The following species are reduced to synonymy: P. neumanni hirstielli Abdussalam, 1941 (= P. neumanni Berlese, 1910), P. rubicundum Lawrence, 1958 (= P. agamae agamae Peters, 1849). Three subspecies and two species are described for the first time, namely, P. fimbriata problematica, P. melanum angolae, P. melanum capensis, P. benguellae and P. spinosa. A list of parasitized lizard species with their scale-mite parasites is presented together with unparasitized lizard species of the Gerrhosauridae and the agamid genera Calotes and Agama. Support is given to Lawrence's (1936) conclusions on the factors preventing parasitization of the lizards. This is followed by a brief discussion of host-parasite relations and similarities between different species are evinced.

Sincere thanks are tendered to Dr A. J. Hesse, Chief Entomologist, South African Museum, for the loan of paratype material of many species; to Dr R. F. Lawrence for making available slides of P. fimbriata, P. (G.) gerrhosauri and co-types of P. rubicundum; to Dr G. O. Evans, British Museum (Nat. Hist.), for advice and for the loan of Hirst's material of P. agamae, P. persicum, P. neumanni and P. inermis; to Mr J. C. Battersby and Miss Alice Grandison of the Reptile Section of the British Museum (Nat. Hist.) for facilitating the collection of parasites from the lizards under their care; and finally to Mr T. E. Hughes and Dr F. A. Turk for their invaluable advice and encouragement.

Dujardin (1835) was the first to describe an adult gregarine occurring in an earthworm. This description contains illustrations of a typical Nematocystis species (Dujardin's Text-figs. B1-B7 and C1 and C2). Subsequent workers made many other observations, but it was Hesse (1909) who first carried out a comprehensive study of these parasites. It was Hesse's excellent work which laid the foundation for succeeding students of the group, the more important of whom are Cognetti de Martiis (1911, 1918, 1920, 1921, 1923, 1925, 1926, 1927), Berlin (1923, 1924), Bhatia (1924, 1924b, 1929, 1930), Bhatia & Setna (1926), Setna (1927), Bhatia & Chatterjee (1925), Troisi (1933, 1940), Tuzet & Loubatières (1946, 1948) and Loubatières (1947, 1948, 1949). Hesse gave a good historical resumé of the work carried out until 1909, while Loubatières (1949) has given a complete and very useful resumé of the work since.

1. The hatching of N. battus under laboratory conditions was investigated. A high hatch of ripe eggs was obtained on exposure to constant temperatures in the approximate range 8–15° C., and very little hatching took place at temperatures outside this range.

2. These, and other published results can be explained in terms of a hypothesis transferred from the study of the breaking of insect diapause. This hypothesis supposes that two processes underly the completion of hatching—a cold process with low temperature optimum and a warm process with a higher temperature optimum and which can only proceed as the cold process is completed.

3. It is not easy to apply these findings directly to field events, but the attempt to do so leads to the suggestion that the apparent synchrony of hatching and the presence of susceptible lamb hosts in the north-east of the British Isles may be partly fortuitous, and that in slightly different climatic circumstances many eggs might hatch in the autumn or during the winter.

I wish to thank Mr A. V. Cunningham of Threepwood, Galashiels, and Mr J. M. M. Cunningham of the Edinburgh School of Agriculture for their generous help in making sampling of their flocks possible, and Dr J. T. Stamp for advice on the presentation of this paper.

The genus Hysterocineta Diesing, 1866, is a small genus comprised, until the present description, of only four species. Together with the genus Ptychostomum Stein, 1861, it forms the family Hysterocinetidae Diesing, 1866, which is a constituent family of the suborder Thigmotricha Chatton & Lwoff, 1949. The holotrichous ciliates belonging to this genus are characterized by the possession of elongate, flattened, flexible bodies possessing an inverted V- or U-shaped sucker at their antero-ventral margins, and a cytostome and cytopharynx at the posterior end.

Opisthogynidae fam.nov. is erected for a group of Gastrocotyloidea Price (1959), in which the gastrocotylid clamps are limited to the four primary pairs, the ovarian field is posterior to the main testicular field, and the cuticle is finely plicated, producing forward-pointing serrations along the margins of the hind body. Opisthogyninae subfam.nov. have a slightly asymmetrical haptor due to unequal lengths of clamps and their pedicels, or to one row being sessile on glandular pads which may be confluent as a thick shelf on one side only. The clamps have an incipient internal asymmetry, the adaxial sector being the more developed. Opisthogyne keralae gen. et sp.nov., on Sphyraena acutipennis: with subequal clamps unequally pedunculated, retains the protohaptor with three pairs of anchors; the muscular penis opens in a lateral atrium, and the median dorsal vagina is unarmed. Gemmaecaputia corrugata Tripathi, 1959, and G. brinkmannii sp.nov., both on Sphyraena obtusata, have each a very conspicuous pre-oral gland-mass. They have unequally disposed and asymmetrical clamps on stalks but lack a protohaptor and anchors. The genital terminalis is similar. The genotype Gemmaecaputia corrugata is redescribed. The new species G. brinkmannii differs in having some post-ovarial testes, in the muscular penis being less heavily cuticularized and the egg being smaller; yet it is nearly twice the size of the genotype, and its pre-oral glands are in two groups of two rows, instead of a single continuous row. Both Allodiscocotyla chorinemi Yamag., 1953 and A. diacanthi sp.nov., occur on Chorinemus sanctipetri. In both of these, unlike the last two genera, the asymmetrical clamps have ribs in the walls. One row of clamps is sessile, on a shelf, or on separate pads, and the other is short-stalked. The protohaptor is retained by the adult. There is a median spiny eversible cirrus and a single lateral unarmed vagina. The genotype is redescribed from a new host. The new species differs in its four separate clamppads on one side, the opposite row being subsessile. There is only one pair of anchors (the largest) instead of three pairs; there are no par-ovarial testes (all are preovarial), and the internal details of the clamps differ. Pseudomazocraes Caballero & Bravo Hollis, 1955, is compared with and included in the Opisthogyninae. Pentatrinae subfam.nov. is erected for Pentatres sphyraenae Euzet & Razarihelisoa, 1959, since its gastrocotylid clamps are modified like those of Priceinae (Gastrocotylidae), but are internally symmetrical and disposed in an asymmetrical fringing-arc round the hind body; the three larger clamps are pedunculated. The muscular penis and atrium are sublateral. Vallisiinae Price, 1943, is emended to include only Vallisia and Vallisiopsis, with highly developed somatic asymmetry. Slight asymmetry is seen in the short-stalked clamps which are usually shifted backwards from the sessile row, the clamps of which are either near three marginal tabs separated by glandular clefts, or on four pads. The clamps themselves are symmetrical and gastrocotylid with ribs in the walls, but without extra effective sclerites. The protohaptor is broad and has one pair of anchors. In all there is a long median spiny eversible cirrus. Vallisia indica sp.nov. from Chorinemus sanctipetri, has sessile clamps on four separate pads and is nearest to Vallisia chorinemi Yamag. This latter, however, has three marginal tabs for the sessile clamps and the combs in the two lateral vaginae are different. V. indica has only half the number of testes and lacks oesophageal diverticula.

Protomicrocotyloidea sup.fam.nov. is created and defined to include aberrant discocotyline forms in which the protohaptor is secondarily developed as a main holdfast. This is a transverse musculo-glandular organ retaining the three dissimilar pairs of larval anchors. The other main holdfast is the unique posteriorlateral glandular pit with projecting muscular lips, just anterior-dorsal to the relatively feeble clamps, which may be gastrocotylid or discocotylid, some always being inhibited. Carangixenus gen.nov. erected for Protomicrocotyle celebensis Yamag., 1953, shares Protomicrocotylinae with Protomicrocotyle mirabilis (MacCallum), since both have gastrocotylid clamps, but in the former they have additional sclerites and an asymmetry approaching that of Gotocotyla spp. (Gastrocotylidae). In Abortipedinae subfam.nov. the muscular protohaptor has anchor-like lobes at each end as in Protomicrocotylinae, but the four clamps on the uninhibited side of the euhaptor are simple discocotylid and without ribs in the capsule walls. The genital terminalia are similar, though the testes, always mainly pre-ovarial, are far more numerous. Abortipedia indica gen. et sp.nov., from the gills of Caranx hippos, differs from the second species Abortipedia pacifica (Meserve) comb.nov. in details of the clamps, in the lack of oesophageal diverticula, and in its uniquely convoluted ovary. The spines of the lateral genital atrium and penis, and those of the lateral vaginal plaque also, are different, and so are the hosts and geographical locations. Lethacotylinae subfam.nov. has been erected for Lethacotyle Manter & Prince, 1953, in which all the clamps are inhibited, and Bilateracotyle Chauhan, 1945, in which only the anterior pair of the four primary pairs is inhibited. In the latter, the clamps are simple and discocotylid. In both genera, the protohaptor is a large wide hemispherical musculo-glandular organ constricted off from the hind body, and is provided with a plicated cuticle, and bears the three characteristic pairs of anchors; and again in both genera, the posterior-lateral funnel-like organ is particularly prominent. The Protomicrocotyloidea are unique in the higher Monogenoidea in using parts of the body as holdfasts which therefore tend to be substitutes, functionally, for the clamps; they are unique with the doubtful exception of Osphyobothrus Yamag., 1958, in showing a secondary development of the protohaptor.

I would like to thank, sincerely, Miss Nora G. Sproston for maintaining our correspondence and for the exchange of ideas on the present subject and particularly for her collaboration in the last section ‘Relationships of the Protomicrocotyloidea’; Dr N. K. Panikkar for providing facilities for my investigations at the Central Marine Fisheries Research Station, Mandapam Camp, and Dr C. C. John, for permission to collect material from the Marine Biological Laboratory of the University of Kerala, Trivandrum.

In this paper three new species of the genus Allocreadium Looss, 1900, viz. A. dollfusi sp.nov., A. singhi sp.nov. and A. hirnai sp.nov. are described. These parasites were obtained from the intestine of the fish Barbus tor (Ham.) brought from the River Hiran. A number of specimens of this species of fish were several times examined for helminth parasites at Katangi, 24 miles from Jabalpur and at Sihora, 25 miles from Jabalpur. These parasites were recovered from different individuals of the fish B. tor (Ham.).

1. The mouse and rat (an abnormal host) show an age resistance towards experimental infections with N. dubius.

2. This resistance was complicated by a different reaction in the male and female mouse and rat.

3. The rat exhibits age resistance despite being gonadectomized immediately after weaning.

4. Gonadectomy with replacement of the homologous sex hormone did not materially alter the age resistance of the host, but the administration of testosterone to the castrated male rat increased the numbers of larvae which penetrated the gut wall. Oestradiol decreased these numbers in the spayed female rat.

5. The relationships between the age resistance and the sex resistance of the hosts was discussed.

The metacercaria of Holostephanus lühei Szidat (1936) is described together with comments on both its linear and tissue distribution within the host (Gasterosteus aculeatus L.), host-parasite reaction and numbers of cysts in relation to the size of the fish.

The adult of Holostephanus lühei Szidat (1936) (syn. H. bursiformis Szidat, 1936) obtained experimentally from the duck and pigeon, is re-described in detail. It is noted that this species is amphitypic and it is suggested that H. dubius (Szidat, 1936) (syn. Cyanocotyloides Dubius, Szidat, 1936) should be reduced to synonymy with H. lühei.

Grateful acknowledgement is expressed to Dr G. Dubois for his interest, advice and valuable opinions given in connexion with this study.

The epidemiology of coccidiosis involving Eimeria perforans, E. media, E. stiedae, E. irresidua, E. magna and E. piriformis was studied for a period of 35 months in a free-living population of wild rabbits, confined to an experimental enclosure.

Relations between the seasonal fluctuations of the above species, on the one hand, and severity of infection and age and social status of hosts, on the other hand, based on the oocyst counts from 2326 faecal samples collected at regular monthly intervals, are indicated.

Mortality within the population was analysed, and coccidiosis was found not to be responsible for the general mortality pattern.

Thanks are due to Mr M. Dudzinski of the Division of Mathematical Statistics, C.S.I.R.O., Canberra for statistical analysis of the data. Mr H. McL. Gordon and Dr J. C. Boray of MacMaster Laboratories, C.S.I.R.O., Sydney, and Dr W. L. Nicholas, of the Australian National University, Canberra, read the manuscript and offered many helpful suggestions. Messrs E. R. Hesterman and D. Purchase of the Wildlife Survey Section, C.S.I.R.O., Canberra, provided valuable technical assistance.

1. The mouse is more susceptible to infection than the rat.

2. The male in both the rat and the mouse is more susceptible to infection than the female.

3. The development of the worm is slower in the male rat than in the female. This relationship does not occur in the mouse.

4. The ecological position of the adult parasite was different in the mouse and rat, the worms living further down the intestine in the rat.

5. The effects of host species on infection of N. dubius are discussed.

1. The life history of Hymenolepis farciminosa (Goeze), first reported in 1955, has been described.

2. The grasshoppers Acrotylus humbertianus Sauss., Acrida exaltata Walk., Oedaleus abruptus Thunb., Crotogonus sp. and Aiolopus sp. were found, experimentally, to serve as intermediate hosts. The cysticercoid has been described and figured. A crow was experimentally infected with the cysticercoid and the adult tapeworm recovered.

The authors wish to express their gratitude to Mr L. Sahai, M.Sc., M.R.C.V.S., the then Director of the Institute, for providing the requisite facilities, and to Dr H. D. Srivastava, M.Sc., D.Sc., F.N.I., Head of the Division of Parasitology, for valuable advice. They are grateful to Dr B. P. Uvarov, Director, Anti-Locust Research Centre, London, and to Dr A. P. Kapoor of the Zoological Survey of India for the identification of the insects.

Representatives of a total of twenty fish species, most of them marine, from the Black Sea coast in Rumania were investigated. Of these, ten species were found to harbour ectoparasitic trichodinids on their skin and gills. Three of them, Trichodina rectuncinata Raabe, 1959, from Gaidropsis mediterranaeus and Crenilabrus griseus, T. caspialosae (Dogiel, 1940) mihi from Alosa braschnikowi meotica and T. d. f. latispina from Gasterosteus aculeatus, were already known.

Three species could be established as new ones: T. puytoraci sp.nov. from Mugil auratus, M. cephalus and M. saliens, T. raabei sp.nov. from Pleuronectes flesus and T. lepsii sp.nov. from M. auratus. They are clearly differentiated from other species.

The following trichodinids were provisionally classified as forms (including one new one) of T. domerguei, thus enlarging this most complicated Trichodina species: T. domerguei, cf. latispina from Gobius syrman, T. domerguei f.n. maris-negri from Gaidropsis mediterranaeus, and T. domerguei f. partidisci from Mugil cephalus. Other populations of T. domerguei could not be properly classified because of lack of material.

The description of the new species of Tripartiella which have been mentioned in the introduction, will be given in a separate paper.

A short survey on marine trichodinids recorded up to the present is given.

It was found that Lucilia porphyrina Walker lays eggs on living toads (Bufo melanostictus). Larvae hatched out of the eggs in about two days and attacked the region of the upper eye-lids of the toads, where a lesion was produced. The parotoid gland was sometimes attacked. The larvae also infested the sites of injuries on the toads.

The toads thus attacked soon died and the larvae fed on their dead tissues. Mature larvae came out of the carcass within a few days and entered the soil, where they pupated. The adult fly emerged after about 20 days.

The mites known to parasitize the lower respiratory tract of birds are discussed and a host list of the various species is given.

Sternostoma tracheacolum Lawrence, 1948, is redescribed and the variations in specimens from various hosts and localities are analysed. The synonymy of S. castroae with S. tracheacolum is confirmed and S. meddai and Agapornyssus faini are made new synonyms of S. tracheacolum. The specimens found in canaries vary widely according to the origin of the host. Those from South African and Italian canaries are closely related morphologically and present relatively long chelae, while specimens from Belgian and North American canaries have much smaller chelae. An intermediate form is found in a Brazilian canary. S. tracheacolum is thought to use wild birds as its normal hosts since it has been found repeatedly in birds in North America, as well as in other parts of the world, and because its presence in the trachea and lungs in these birds seems to be much better tolerated than in the canaries. Canaries are thus probably infested secondarily, and it seems that Passer domesticus has served in the transfer of the mites between the two groups. The specimens from wild birds present the same variability as those of the canaries, and one can also distinguish three different groups on the basis of the length of the chela. The origin of these variations is discussed. Geographical or biological isolation of the host probably plays a more important role than the host itself in the production of variation.

Hypopi representing probably two species of the genus Falculifer have been found in the air-sacs and lungs of two central African birds. Also Speleognathus poffei, S. striatus and Boydaia sp. have been taken from the lungs or trachea of their hosts in Ruanda-Urundi or U.S.A.

Collection of most North American material was carried out under a research grant (G-11035) from the National Science Foundation.

The authors wish to thank the following for their co-operation and assistance in this study by making available various collections of Sternostoma tracheacolum: E. W. Baker, U.S. National Museum, Washington, D.C.; G. Owen Evans, British Museum (Natural History), London; D. P. Furman, University of California, Berkeley; S. Grétillat, Laboratoire Central de l'Elevage, Dakar; R. F. Lawrence, Natal Museum, Pietermaritzburg; and G. Lombardini, Rome.

A description is given of the external features of the scolex and strobila and the anatomy of the proglottid of Acanthobothrium pearsoni sp.nov. found in the intestine of Orectolobus maculatus Bon. In view of the similarity in host distribution and anatomy to that of Biporophyllaeus madrassensis Subramanian some comments are made on the status of the order Biporophyllaeidea and it is suggested that B. madrassensis may be a proglottid of a species of Acanthobothrium.

1. Seventy-three females, 1 male, 20 nymphs and 1 larva of Ixodes arboricola Schulze & Schlottke, 1929 were found on a juvenile enfeebled starling (June, 1933, Denmark).

2. Range of variability of employed systematic characteristics of this species has been checked, and it was found impossible to preserve the following subspecies of I. arboricola, muscicapae, domesticus and bogatschevi.

3. Between length and breadth of idiosoma of female, and between lengths of legs I and III (excluding trochanter and coxa) the ratio was found to be almost linear. A deformed leg II is described as a case of regeneration.

4. I. arboricola, I. passericola, I. dryadis, and I. strigicola are regarded as synonyms and have all been incorporated in the species I. arboricola, the habitat of which is birds' nests in tree cavities.

For supplying material for this study I wish to thank Professor M. Christiansen, State Veterinary Serum Laboratory, Copenhagen; Dr B. Hubendick, Director of ‘Naturhistoriska Museet’, Gothenburg; Dr S. L. Tuxen, Head of the entomological department of ‘Universitetets zoologiske Museum’, Copenhagen, and Dr Glen M. Kohls, Sanitarian director for the loan of P. Schulze's former collection of ticks.

I am most thankful to Dr Don Arthur, for advice and critical reading of the manuscript.

1. The development of S. duttoni and S. recurrentis was studied in lice.

2. After penetrating the anterior part of the midgut spirochaetes were seen in the haemocoele, haemocytes, neural ganglia and muscles of lice. They were never seen elsewhere.

3. The haemocytes of infected lice sometimes contained coarse granules believed to be the breakdown products of spirochaetes due to phagocytosis.

1. A technique is described for the preparation of axenic cultures of protoscolices of Echinococcus granulosus.

2. Protoscolices removed aseptically from hydatid cysts are treated with 0·02% crystalline pepsin at pH 2·0 for 10 min. at 38°C. in order to remove (a) daughter cyst germinal membranes, and (b) dead or degenerating protoscolices.

3. Protoscolices may be maintained for more than 100 days in a variety of media. These include media containing various proportions of some of the following: chick embryo extract, beef embryo extract, hydatid fluid, bovine amniotic fluid, Parker 199, bovine serum.

4. 10–20 ml. of culture media was used at 38°C., either in roller tubes or shaken in a water-bath. Media were renewed every 48 hr.

5. Protoscolices developed into cysts by two routes, either (a) by becoming vesicular, gradually growing in size, and finally becoming enclosed in a laminated envelope, or (b) by forming a ‘posterior bladder’ which became relatively enormous and ultimately absorbed the scolex region, the whole forming a cyst within an envelope as in (a).

6. In the majority of media, after about 31–48 days' culture, a thin envelope was secreted which developed later into a thick laminated membrane.

7. Cysts with laminated membranes ultimately underwent fatty degeneration and became cytologically abnormal.

8. In the most successful experiments, cells or clusters of cells formed within the cysts and these may have represented the anlagen of the protoscolices.

9. In no case was segmentation, or any other sign of strobilar development, obtained.

10. These results show that the laminated membrane in E. granulosus is initially of parasite origin and not of host origin as believed by some workers to be the case.

11. Since there is evidence from the literature that E. multilocularis does not form such an envelope in vitro, a clear developmental difference appears to exist between the two species.

12. It is suggested that this difference offers an explanation for the formation of unilocular or multilocular cysts. Since E. granulosus secretes a laminated envelope, its development is limited to a single or unilocular type of cyst. In the case of E. multilocularis no such limitation occurs, so that the invasive multilocular type of cyst could more easily develop.

Young chickens given an infection of 5000 oocysts of E. maxima were highly resistant when they were given a 2nd dose 3 weeks later. Immunity in these fowls was not apparent when they were again infected 10 weeks after the 2nd infection. The same fowls given a final dose 26 weeks after the 3rd infection became heavily infected. These observations suggest that immunity developed to this infection is short-lived, and this finding is discussed in relation to the duration of acquired immunity to E. tenella infection in the fowl and E. stiedae infection in the rabbit.

Natural infection with the cephalobid nematode, Daubaylia potomaca, is reported in Helisoma antrosum pericarinatum ( = H. anceps pericarinatum) collected in the vicinity of the University of Michigan Biological Station on Douglas Lake, Cheboygan, Michigan.

The life-cycle of D. potomaca, which appears to be unique, has been determined and reproduced experimentally utilizing Australorbis glabratus and other snails as hosts. The cycle involves escape from the host by gravid females, invasion by the females of new hosts and the reproduction therein of generation after generation of parasites, and the eventual emergence of female worms from dying hosts to the external aquatic environment. The parasite does not lead a saprozoic existence, and no dauer larvae were seen. Except for the newly emerged female, no stage of D. potomaca is ‘free-living’, and there is no evidence that transmission can occur except through the agency of these females. However, parasitic females removed at any time from their hosts by dissection are fully capable of infecting new hosts under experimental conditions.

Dissection of A. glabratus infected with known numbers of female D. potomaca disclosed that the gravid nematodes deposit about two eggs per day in the tissues, that larvae may be found after 5 days of infection, and that the first ‘new’ generation of adult males and females appears within the host 11 or more days after infection. Continued reproduction in the host may give rise to very large nematode populations. A. glabratus exposed to five female D. potomaca usually became infected and all infected snails were killed within 44 days. Death of infected snails was preceded, in nearly every case, by the emergence of female D. potomaca from their hosts. It is suggested that this phenomenon reflects an adaptive response of the worms to changes in the internal milieu of the snail.

Attempts to infect certain physid and lymnaeid snails with D. potomaca failed, and varying degrees of success were achieved in attempts to infect several planorbids. Of the latter, the most suitable hosts appeared to be A. glabratus (Puerto Rico) and Helisoma sp. (Michigan); the least suitable host was Helisoma caribaeum (Puerto Rico and St Croix), in which an intense tissue reaction killed all nematode eggs before they could hatch. Other susceptible planorbids (in declining order of apparent suitability as hosts) were Helisoma trivolvis ? macrostomum (Canada), Bulinus truncatus (Egypt) and Planorbarius corneus (Massachusetts).

Some of the problems associated with the possible use of D. potomaca as a means of biological control for A. glabratus are discussed.

It is a pleasure to thank the persons whose names appear in the text for aid or counsel graciously extended. I am also grateful to Dr George L. Graham (University of Pennsylvania) for certain citations in the literature, to Dr M. R. Tripp (now at the University of Delaware) for receiving the shipments of snails in Boston, and to Dr A. H. Stockard, Director of the University of Michigan Biological Station, for facilitating the field work.