While examining the strongyles of the fourth stomach of an ewe belonging to the Cambridge University Farm, which had been slaughtered for post-mortem examination, numerous male and female Ostertagia circumcincta (Strongylus cervicornis of MacFadyean) were found. A few specimens of Haemonchus contortus were also present.

This paper gives an account of the mature eggs and the miracidium of Paryphostomum mehrai obtained from experimentally infected white rats, which were fed with the cysts of Cercaria mehrai obtained from naturally infected as well as artificially infected snails of the species Indoplanorbis exustus. The metacercariae develop into the adults in the intestine of the host in a period of 20 days, after which the adults begin to lay their eggs, which are passed out with the faeces of the host. The molluscan phase of the life cycle involves the gradual development of the miracidium larva after its penetration into the molluscan host into a mother rediae. The mother rediae, not more than three to five in number, were observed in the preoesophageal region of the snail host. They produce large numbers of daughter rediae, which were found migrating towards the liver mass. The daughter rediae, after fixing themselves in the liver mass, undergo further development and produce large numbers of cercariae. The entire process, from the entry of the miracidium until the cercariae are matured takes about 8 weeks.

Psilochasmus oxyurus, type species of the genus Psilochasmus Lühe, 1909, has been redescribed from whole mounts and transverse, horizontal and sagittal sections. Twenty-five worms from one common mallard, Anas platyrhynchos L. and 12 from one greater scaup, Nyroca marila L. are considered as conspecific with P. oxyurus, although they show some variations in body size and shape of the testes. Of the other eight known species of Psilochasmus, five have already been synonymized and the remaining three, namely, P. indicus Gupta, 1957, P. alii Jaiswal, 1957, and P. megacetabulus Jaiswal, 1957, are declared synonyms of P. oxyurus.

Experiments to investigate the metabolism of glycine, L-glutamic acid and L-aspartic acid by Moniliformis moniliformis were carried out by incubating adult worms aerobically for 3 h at 37°C in Tyrode's solution containing either [U-14C]glycine, L-[U-14C]glutamic acid, L-[U-14C]aspartic acid or L-[4-14C]aspartic acid. Much of the glycine and glutamic acid was absorbed by the worms, but little of either was metabolized. Aspartic acid was readily taken up and metabolized. After incubating with L[U-14C]aspartic acid, most radioactivity was found in ethanol and a volatile compound, presumed to be carbon dioxide, with smaller amounts in lactate, alanine, acetate, malate, glucose and succinate. After incubating with L-[4-14C]aspartic acid, most radioactivity was found in lactate and the presumed CO2 with small amounts in alanine, malate and succinate. No radioactivity was found associated with ethanol or acetate. Possible metabolic pathways and suggestions for a relationship between the metabolism of aspartate with that of alanine and serine in this parasite are discussed.

The different types of malaria pigment occurring in oocysts of naturally infected Anopheles caught in human dwellings at Kampala, Uganda, are described and figured (selection from 204 camera lucida drawings).

The exact significance of each particular type of pigment is uncertain and in the present state of our knowledge it is not possible to do more than to place them tentatively into four groups and to indicate to which species they probably belong.

The genus and species of Lygaeidae described and figured herein was obtained with several others from a squirrel's nest at Kodera, S. Nyanza Province, Kenya, East Africa, by Dr Garnham, Professor of Medical Protozoology at the London School of Hygiene and Tropical Medicine.

In the foregoing paper Dr E. P. Snijders has described the oöcysts of a species of Eimeria which he found in the stools of a patient under his care in Medan (Sumatra). The manuscript of this paper, together with a preparation containing the cysts in question, was kindly sent to me by the author with the request that I would “be so kind as to add my opinion, and give to the species its right name.” I shall do my best to comply with both these requests in the present note.

The adenosine nucleotide and adenylate energy charge values of Nematospiroides dubius and Trichostrongylus colubriformis maintained in vitro under aerated and under near-anoxic conditions have been measured. Maintenance of the nematodes in both conditions had an adverse effect on their energy metabolism, but in comparing these effects it was found that the changes were more significant in those nematodes maintained in near-anoxic conditions and that the changes were more apparent in male nematodes. The smaller changes in the energy charge values of female worms, particularly N. dubius where there was no difference between worms in aerated conditions and those in near-anoxic conditions, were explained by the presence of eggs in the nematodes. At no time did the energy charge of nematodes in near-anoxic conditions fall below 0·50 but, whereas nematodes in aerated conditions were able to continue moving throughout the experiment, those in near-anoxic conditions stopped moving during the first 3 h. It is suggested that in the absence of sufficient oxygen the nematodes were able to maintain their energy charge above 0·50 by removal of AMP from the adenylate pool, resulting in the depletion of their total adenylate. The changes in the energy charge and behaviour of the nematodes are related to the survival of the nematodes in the oxygen-deficient environment which they inhabit in vivo.

Agrippina bona, a gregarine parasitic in the gut of the larva of the rat-flea Ceratophyllus fasciatus, was first described by Strickland in 1912. His account of the sporulation of the gregarine was so curious that a more detailed investigation has been undertaken, which has given rise to the present paper. The work has been done in the Quick Laboratory, under Professor Nuttall, to whom I wish to express my thanks for the interest he has taken in my researches, and for his constant encouragement.

Generic Diagnosis, ♀. Cephalothorax with transverse lateral expansions, small in young, resembling a hammer in old specimens, between whose anterior surfaces projects the head. Neck smooth, cylindrical and without swimming feet. Trunk much enlarged transversely, smooth, flattened dorsiventrally, bearing a pair of posterior appendages profusely and dichotomously branched. Abdominal appendages reduced to two small knobs; or one undivided abdomen.Egg-strings long and straight; eggs multiseriate. Two pairs of antennae, twopairs of maxillae, one pair of maxillipedes.

The systematic position of the blood-sucking Gamasides Leach, 1815, is still very unsatisfactory. In his work on external parasites, Ewing (1929) recognizes the two families Parasitidae and Dermanyssidae, distinguishing them chiefly by the form of the chelicerae. The former family to which Laelaps and related genera belong is defined by Ewing as follows: ‘chelicerae of a generalized type having the tips incurved and being provided with teeth, and the fixed arm usually bearing a seta near its tip’. The Dermanyssidae have modified chelicerae, ‘usually without teeth and fixed arm always without setae’. In this family Ewing puts the genera Liponyssus, Dermanyssus and related ones.

In September, 1930, Dr E. C. Faust brought back from the Coto Region of Northern Panama two young female spider monkeys (Ateles geoffroyi). On December 11th one of these died from an experimental infection of Strongyloides stercoralis, and at autopsy was found to be very heavily infested with lice. Previous to this date the monkey had been handled a number of times but no lice noticed, although the two monkeys had frequently been observed carefully examining each other for external parasites. It is believed that the subsequent separation of the two (November 22nd) combined with the victim's illness allowed the lice to multiply at a prodigious rate. The hairs practically all over the body were found to bear nits, frequently as many as three or four per hair. Only a few lice have ever been found on the other monkey in spite of several careful examinations.

During the course of investigations into the distribution and seasonal activity of the tick, Ixodes ricinus L., in South Wales (Edwards & Arthur, 1945), a male tick was recovered which on examination was found to be a member of Ixodoidea, but which differed from the normal male of I. ricinus L. It was recovered from Margam Moors (Glamorgan, South Wales) by one of the writers (D.R.A.) in 1945, whilst dragging a blanket over rough vegetation, a method previously employed by MacLeod (1932) for the recovery of ticks from grassland. This is the only specimen of its kind which has been found, despite the examination of several thousands of males during the past three years. It has therefore been considered desirable to place on record a description of the form. When placed in a tube containing ten unfed females of I. ricinus, no mating occurred. Under similar conditions a typical male of this species mated with one unfed female within 7 minutes of its introduction.

Numerous specimens of this fluke were collected in October 1936 from the small intestine of the Bonell's eagle, Hieraetus fasciatus fasciatus, shot in the vicinity of Allahabad. Only one out of six hosts examined was infected. The sexually mature worms, 1·171–2·622 mm. long, are distinctly divided into elliptical forebody and cylindrical somewhat posteriorly pointed hindbody. The forebody, 0·969–1·236×1·186–1·476 mm., with foliate lateral margins united behind the holdfast Organ, is armed with very minute, backwardly directed spines; the hindbody is 1·2–1·386×0·634–0·818 mm. The length ratio of fore and hind parts is approximately 6:7.