Attempts to repeat the isolation of an ecdysone-like steroid from Biomphalaria glabrata revealed that some of the manipulations described by Muftic (1969) were physically impossible to repeat. With modified procedures no ecdysone-like steroid was found. The original publication gives scant attention to certain experimental details. Some sections of the text bear very close resemblance to earlier publications by different authors. The amount of substance claimed to have been isolated, and the long survival period claimed for Schistosoma mansoni larvae in vitro, are claims which, amongst others, seem highly unlikely a priori. All attempts to contact Muftic have proved to be futile. It is suggested that the paper is, at least in part, erroneous and that any future reference to it should clearly indicate its suspected invalidity.

Despite these results, it is considered likely that future investigations will demonstrate physiological roles for steroids in snails.

I wish to acknowledge the stimulating communications of Drs E. L. Hansen, M. Voge, R. E. Thorson, C. S. Richards, J. N. Kaplanis, G. Nace, R. Monroe, and of E. Chernin, who first brought this matter to my attention. Theanalytical steroid work could not have been done nor interpreted without the considerable time and effort willingly given by Drs F. Kohen and R. Counsell of the University of Michigan College of Pharmacy. My snail populations were supplemented with snails from the tanks of Mrs B. Caveny. Technical help was given by E. Perisho, G. Lindsay and P. LoVerde. Financial support was kindly provided by Dr J. B. Burch. This investigation was supported in part by the United States-Japan Cooperative Medical Science Program administered by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health, Department of Health, Education and Welfare, grant N.I.A.I.D. AI-7364, and in part by NSF grant GB-29315. Improvements were made to the first draft of the manuscript after it was critically read by Drs E. L. Hansen, F. Kohen, M. Voge, E. Chernin, R. E. Thorson and J. N. Kaplanis.

Thirty-five lambs (14 weeks old), the progeny of Border Leicester rams mated with Border Leicester × Merino ewes were divided at random into two groups. Seventeen lambs received 3500 Haemonchus contortus larvae at weekly intervals (weekly group) and 18 lambs received 500 larvae each day (daily group). The dosage was decreased to 1400 and 200 larvae respectively after 8 weeks.

The daily infection with a small number of larvae induced a severe anaemic condition with the blood picture falling to 7% PCV; 2% Hb conc. and 1·6m/mm3 RBC count in 78 days. The anaemia with weekly dosing of larvae was less severe with equivalent figures of 10–12% PCV; 4% Hb conc and 3·6m/mm3 RBC count.

Two phases were observed in the changes in the sodium (Na+e) and potassium (K+e) electrolyte concentrations. In the first phase (K+e) increased and (Na+e) decreased, while in the second phase both electrolytes increased. The influx of young red blood cells into the circulation is considered as the factor responsible for these changes.

Adult desert locusts were experimentally infected with a dose of 50 M. nigrescens ova and larval nematodes removed 14, 17, 21 and 24 days afterwards for in vitro radiotracer studies. These nematodes were incubated under controlled conditions either in a nutrient medium or in insect saline, which contained the appropriate 14C or 3H-labelled radioisotope. The rate of incorporation of the radioisotope into the proteins of the nematode was measured.

The rate of incorporation of 14C-leucine into proteins was greatest for the 17- day-old larvae and this accorded with the in vivo growth pattern of the nematode. This isotope was incorporated less rapidly into proteins by the 14-, 21 and 24-day- old larvae, which synthesized proteins at approximately the same rates as each other. A non-linear rate of incorporation was manifest for each of the larval stages.

Total dry weight and protein determinations showed that the nematode synthesizes relatively large quantities of non-proteinaceous reserves during the third week of infection, whilst proteins are preferentially synthesized between the 21st and 24th days of infection.

The 17-day-old nematode larvae were able to incorporate six 14C-amino acids into proteins to varying degrees. Leucine was incorporated most effectively into nematode proteins, whilst glutamic acid was the least incorporated of the six amino acids.

These nematode larvae could not effectively metabolize the 3H-dipeptide histidyl-leucine and incorporate its component amino acid residues into proteins. Similarly, a preparation of 3H-haemolymph proteins were not significantly metabolised and incorporated into proteins by the nematode. However, the nematode metabolized and incorporated an exogenous source of 14C-glucose into proteins at relatively high levels.

Incorporation of 14C-luecine into proteins was seven times more rapid for nematodes incubated in buffered insect saline than for those incubated in a more complete nutrient medium.

The dietary requirements of the nematode for protein synthesis were discussed in relation to their associated effects upon the host metabolism and an active transport of dietary amino acids into the nematode was postulated.

We wish to thank Dr H. L. Speer and Dr K. K. Nair for their helpful suggestions regarding radioisotope techniques. Thanks are also due to the National Research Council of Canada for providing financial assistance (Grant No. A4679).

Forty-five cattle, which had recovered from EOF and been kept free from reexposure to infection for periods of 1–43 months, were given a single uniform lethal challenge using a stabilate prepared from triturated infected ticks. All withstood the challenge which killed the five controls. There was an increase in the incidence of mild febrile reactions with time since last exposure to T. parva, indicating a gradual loss of immunity in the absence of reinfection. The duration of the immunity was not related to the severity of the initial reaction.

We are indebted to our colleagues on the Immunological Research on Tickborne Cattle Diseases and Tick Control Project, with whom we designed and carried out the experiment.

It has been demonstrated that Hymenolepis microstoma in mice treated with cortisone grow larger than those in control mice.

The possibility of this being an immunosuppressive or growth-stimulating effect is discussed since the results from two strains of mice are different.

Antibody production is suppressed in the cortisone-treated animals and it is suggested that the circulating antibody normally affects a partial rejection of the worm.

I am grateful to Professor C. A. Hopkins and Dr T. S. C. Orr for many helpful comments during the course of this work and especially to Professor C. A. Hopkins for the facilities which he has placed at my disposal. Many thanks also to Miss Gillian Moore and Mr Jack Keys for their expert technical assistance. This work was in part supported by a grant from Fisons Pharmaceuticals Ltd.

An analysis of the course of infection of mixed oral infections of 12 cystacanths of Moniliformis dubius in 174 male and 179 female Wistar rats has been undertaken.

There was a marked decline in the average recovery rate of worms of both sexes from hosts of both sexes during the course of the infection.

Female worms from both male and female rats showed, on average, a greater power of survival than male worms from the third period (10–13 weeks) onwards.

Male rats were found to retain, on average, a greater number of worms of both sexes than female rats.

We wish to thank Miss Susan Arnold and Mr David Barnard for excellent technical help.

In the winters of 1969 and 1970 a total of 64 rabbits was shot at 11 sites covering diverse climatic regions in the western, central and eastern districts of New South Wales. The ectoparasites of these rabbits were identified and counted. The flea Echidnophaga myrmecobii was most frequently found in western districts; the louse Haemadipsus ventricosus was prevalent in the central districts; the mite Listrophorus gibbus was very abundant on rabbits from the eastern districts, whilst the mite Cheyletiella parasitivorax was prevalent on rabbits from central and eastern districts.

The probable consequences of these variations are discussed in relation to their possible effects on the epidemiology of myxomatosis.

This investigation was carried out as part of the study of the biology of the wild rabbit undertaken by the Division of Wildlife Research, CSIRO, under the general supervision of Mr K. Myers. The author is indebted to P. Haycock and Miss S. Stephens for invaluable technical assistance. Messrs I. Parer, M. Stranger, G. Richards, H. Bults, J. Libke and P. Haycock shot the rabbit samples.

A large Babesia species was found in a leopard (Panthera pardus) in Kenya. It was established in domestic cats but no other animal was found to be susceptible. The parasite has been compared with other piroplasms of felids and it was found to differ from them in some significant characters. It was established as a new species and named Babesia pantherae.

We would like to thank Miss B. O. Vidler for her assistance, Dr S. F. Barnett for many helpful discussions and Professor N. D. Levine for pointing out the need for this description.

The parasite was isolated when we were working at the East African Veterinary Research Organization at Muguga in Kenya and we are most grateful to that organization for facilities.

The writer (Sprent, 1971) described four female specimens of an ‘ascaridoid’ nematode from a vial labelled ‘Tasmanian Marsupial Wolf’. The name Cotylascaris thylacini was proposed, in spite of there being no male specimens available. This was because no other genus among ascaridoids was known by the writer to possess cup-like cuticular structures on the margins of the lips and also because the thylacine (Thylacinus cynocephalus) is considered to be on the verge of extinction, if not extinct already.

The transformation of cercariae of Schistosoma mansoni into schistosomula has previously been achieved by passage through membranes of biological origin. This transformation has now been effected in the absence of a membrane. Chemical stimulus for transformation results from contact with human or rat skin lipid and fractionation of the latter led to localization of the active component in a fraction containing phospholipids. The series of processes involved in transformation was subsequently found to be set in motion by the action of egg lecithin-water mixtures on an aqueous suspension of cercariae and yields of 90% of live schistosomula may be obtained reproducibly with crude egg lecithin-water in the ratio 1:50. The juvenile worms were found, by accepted criteria, to be identical to those produced by the normal penetration procedure. Purified lecithin does not produce the same stimulus and the effect of the physical state and of possible impurities present in crude egg lecithin is discussed.

This work was supported by the Conselho Nacional de Pesquisas (Brazil), the Banco Nacional de Desenvolvimento Econâmico FUNTEC contracts nos. 99 and 110 (Brazil), U.S. Army Grants nos. DAHC-19-70-G-0017 (to B.G.) and DAHC-19-70-G-0070 (to J.P.) and by the FORGE Foundation. Contribution no. 18 from the Schistosomiasis Research Unit, Institute of Biological Sciences, Federal University of Minas Gerais, Brazil.

This study examines the ultrastructure of the posterior vacuole in frozen-etched spores of Thelohania bracteata (Nosematidae), a microsporidian infecting the fat body of larval black-flies (Simuliidae). This organelle, considered important in providing intrasporal pressure for sporoplasm extrusion through the polar filament, has a double membrane with particles on its internal faces as revealed by the freeze-etching technique. The size and pattern of these particles differ from those in membranes of the polar filament and nucleus, and this difference may have functional significance. The posterior vacuole, and also the polaroplast, may originate from expanded sacs that occur in the immature spore. There is evidence from this study that there are many basic ultrastructural similarities between spores of different microsporidian species and that at least some reported differences are the result of varying techniques.

We gratefully acknowledge the freeze-etching facilities provided by the Department of Pathology, Faculty of Medicine, McMaster University. The research was supported by Grant A-130 from the National Research Council of Canada.

Biochemical studies on the non-specific phosphomonoesterases of Fasciola hepatica have shown the presence of acid phosphomonoesterase active at pH 4·6 and two forms of alkaline phosphomonoesterases active at pH 7·6 and pH 9·6 respectively. Histochemical studies have located acid phosphomonoesterase in the walls of the intestinal caeca and to a lesser extent in the tegument. Alkaline phosphomonoesterase was found to occur mainly in the excretory ducts and to a lesser degree in the uterine wall. Glycogen was mainly concentrated in the yolk glands, parenchyma, mature eggs and the non-muscular regions of both oral and ventral suckers.

Dr A. J. Probert takes pleasure in recording the support of the British Council and the Indian University Grants Commission to enable him to study in India.