Two new species of coccidia belonging to the genus Wenyonella are diagnosed here by the characters of their oocysts. Wenyonella uelensis and W. parva are geographically related (Uele, Belgian Congo) to the type species, W. africana Hoare (Uganda). By their hosts, two rodents of which one is a terrestrial squirrel, one can relate them to the second species, W. hoarei found in an Indian squirrel by Ray & Das Gupta. W. uelensis is sharply differentiated from the two previously known species, W. africana and W. hoarei, by its oval form, whilst W. parva is noticeably smaller.

An investigation was made of certain aspects of the physiology of nematodes from the alimentary canal of sheep.

Cellulose digestion has apparently no effect on the nematodes.

The composition and concentration of a physiological saline solution suitable for Ostertagia circumcincta—and possibly for the other species—was determined.

The effect of acidity on the intestinal worms showed that they could not live in the abomasum because the acidity in this chamber would be too great. O. circumcincta could not inhabit the stomach of horses, and carnivores, or the abomasum of cattle, in all of which the acidity reaches a level lethal to this species.

A graph is given showing the distribution of the nematodes in the small intestine of the sheep. After a study of the effect of bile salts on the different species its influence in determining this distribution is discussed.

A discussion of the evidence relating to the food of nematodes of the alimentary tract led to the conclusion that even species with rudimentary buccal capsules might suck blood; on the other hand, the results from the benzidine tests and spectroscopic examinations indicate that the haemoglobin demonstrated in nematodes is synthesized by them.

It was shown that O. circumcincta does not probably feed on abomasal contents. Bacterial difficulties hampering these experiments were overcome by using an apparatus whereby the contents of the abomasum could be percolated over the worms. The latter had been surface-sterilized with acriflavine solution.

All attempts to feed the nematodes on serum, defibrinated blood, and blood digests failed. Bacteria again constituted a difficulty, but it is suggested that the failure is not entirely due to them, and that perhaps the tissues of the host must be incorporated into the media.

1. The so-called parasitic dinoflagellate occurring in the gut of the polychaete worm Scolelepis fuliginosa Clpde. is described and is shown to be the sexual phase of the gregarine “Selenidium foliatum” Ray.

2. The gametocytes (often very unequal) associate by their posterior ends while in situ. One remains attached and its epimerite is transformed into a foot-like organ serving to attach the gametocyst to the host throughout the rest of development. The gametocyst is elongate and pyriform (26−226 × 9−34 μ) and its formation involves very little alteration in the shape of the gametocytes. Solitary encystment also occurs.

3. The first gametocytic nuclear division is described. Forerunners of the gamete nuclei are formed within the nuclear area of the gametocyte. Flagellated isogametes are formed. There is no residuum.

4. The spores are spherical, averaging 8·5μ in diameter, the number depending on the size of the cyst enveloping them. When ripe, they contain four or eight spindle-shaped sporozoites 9·4−14 × 2−3·75μ and, in vivo, a central, spherical, refrigent residuum.

5. A new genus Selenocystis is proposed for this organism, with S. foliata (Ray) as the type species. Although I have not found its asexual phase, the probability is that it may still be classified among the schizogregarines.

The parasites described in this paper were taken from twelve specimens of the Natal horseshoe bat (Rhinolophus geoffroyi zuluensis) found in a cave near Wartburg, Natal, in May 1937. Thirteen specimens of the parasite were taken from the vibrissae situated on or near the nose-leaf of the host, each of them being attached near the base of one of these tactile hairs. No single vibrissa was found to have more than one parasite attached to it. The largest number of mites taken from any one host animal was four, the smallest was one, and none were found on any part of the body other than the facial region. With the aid of a hand lens the parasites can easily be seen clinging to the nasal vibrissae, where they appear as minute white specks. So far as I am aware mites of the family Listrophoridae have not previously been described or recorded from South Africa.

1. Three species of flea were found on rats caught on the docks of Plymouth, England, namely, Nosopsyllus (Ceratophyllus) fasciatus, Xenopsylla cheopis, and Leptopsylla segnis (musculi).

2. The findings of Xenopsylla cheopis were almost entirely confined to a certain grain store, whence the flea was obtained constantly throughout the period of the investigation.

3. A few rats caught in the town of Plymouth yielded Leptopsylla segnis and Nosopsyllus fasciatus, but no Xenopsylla cheopis.

Various stages in the life cycle of Panopistus pricei are reported from Agriolimax agrestis. These are essentially the same as those reported by Krull from Zonitoides arboreus. The excretory system of a developing metacercaria is described.

The effect of an efficient bactericidal solution on the hatching of Haemonchus eggs was studied and it was found that a large proportion remained viable. Based on former work, a medium was devised in which the bacteria-free eggs hatched and the larvae developed to the infective stage. These larvae were morphologically and otherwise normal, except that they were slightly smaller than faecal-grown specimens, although the size ranges overlapped. Infection tests proved that Haemonchus larvae grown under conditions of sterility were normally infective for, and produced normal adults in, a susceptible lamb.

A Collection of ticks from British Somaliland recently sent to the British Museum (Natural History) contained specimens of a species of Ornithodoros unlike any in the national collection and (from the appearance of the integument) related to the North African species O. foleyi Parrot (from Algeria) and O. delanoëi Roubaud & Colas-Belcour (from Morocco). The late Prof. G. H. F. Nuttall presented to the Museum a specimen of O. foleyi, and the writer is indebted to Prof. E. Roubaud for comparing one of the present specimens with the type of O. delanoëi. Prof. Roubaud writes to say that, having examined the Somaliland specimen, he and M. Colas-Belcour are of the opinion that it belongs to the species O. delanoëi: and that the various details of structural difference do not warrant a specific distinction, but indicate that the present specimens may belong to a different biological or geographical race. The large size of these Somaliland ticks, the discovery of their larvae and their presence in a locality so widely separated from that of the type, are considered important enough to be placed on record, and the specimens are regarded as representing a subspecies of O. delanoëi

The species of Hymenolepis Weinl. described in the following pages was collected from the small intestine of a greater black-backed gull, Larus marinus, shot on the Dovey mudflats near Aberystwyth, in February 1935. Comparisons of the dimensions of scolex and strobila, measurements of rostellar hooks and suckers, and appearance of genitalia, prove beyond doubt that the species is identical with that described by Linton (1927) under the name of Hymenolepis fusus (Krabbe) (vide Table infra). From the data tabulated in the discussion below, the writer is satisfied moreover that the species described by Linton is totally distinct from Taenia fusus Krabbe 1869, and the new name Hymenolepis neoarctica is therefore proposed to include Linton's species. Since the description by Linton dealt only with the morphology of the immature forms, the following account of the morphology of the mature worm is given, based on material collected at Aberystwyth.

Two mature worms of this species were recovered from the small intestine of a Common Snipe, Gallinago gallinago (Liun.), shot on a Cardiganshire moor in July 1935. Three mature worms were again obtained from a Common Snipe shot on the same moor in the third week of October 1936, just prior to the arrival of the migrant snipe.

One hundred and ninety-seven English sparrows collected in the vicinity of Lafayette, Indiana, have been examined for cestode parasites. The species recovered and incidences of infection are as follows: Hymenolepis passeris (Gmelin), 2·5%; Choanotaenia passerina (Fuhrmann) provis, 3·5%; Anonchotaenia globata (von Linstow), 2·5%. Of these, Hymenolepis passeris is reported for the first time from North America. The name Haploparaxis linstowi is proposed for Aploparaksis fringillarum von Linstow nec Rudolphi. Additions are made to the present descriptions of the species observed.

This paper deals with the species of the commonest genus of the American Streblidae. The descriptions of the species were made from specimens mounted on slides, in Canada balsam. Here I wish to point out again that spirit preserved specimens are unsuitable for the study of these Diptera. These specimens do not show clearly the details of the structure of some sclerotized parts, and especially the arrangement of the small setae on the thorax, which in some cases, are the only reliable characters for the separation of the species. The study of unmounted specimens of these Diptera may easily lead to incorrect identification, or to the increase of undesirable synonyms.

Experiments upon the duration of chronic infections of Plasmodium relictum in canaries prove that parasites may persist in the peripheral blood, as ordinary schizogonic stages, up to 8 years and 3 months after infection and that the blood of such birds is infective for clean birds for at least the same period.

1. Diapause in Lucilia sericata is caused by unfavourable conditions during the larval or prepupal period.

2. Diapausing prepupae usually contain a higher proportion of dry matter than do normal individuals.

3. Diapause occurs because the corpus allatum (Weismann's ring) is not producing the necessary hormone.

4. Diapause is ended when prepupae are removed from sand to empty tubes. Probably the corpus allatum is stimulated by a nervous reaction; the reaction is not due to an increase in the rate of metabolism.

5. Low temperatures (5° C.) do not affect the hormone, but high ones (35–37° C.) destroy it.

6. Prepupae of Lucilia sericata have salivary glands which are dilated to nearly a quarter the body size. The contents serve as a store of water during diapause.

7. Diapausing prepupae after desiccation drink water and return to their original body weight. The water increases the volume of blood in circulation, and the blood controls the size of the adult produced.

8. Diapause in nature enables the species to survive unfavourable conditions.