Numerous specimens of this fluke were obtained on several occasions from domestic ruminants which were examined at Mukteswar. It has been ascertained that the infection occurs very commonly among goats and sheep, and occasionally also among bulls. Two buffaloes were also examined for infection with these flukes, but with negative results. The intensity of infection, particularly among ovines, is very great, several hundred specimens being obtained every time. Although these worms are found in all parts of the alimentary canal posterior to the oesophagus, the usual seat of predilection is the small intestine. On one occasion only were a few worms found in the bile ducts. It has been observed that the flukes die soon after the death of the host and begin to undergo post-mortem changes. For this reason it was often found difficult to obtain satisfactorily stained preparations of the parasites. Usually acid haematoxylin gave better results than the various carmine stains. The following description of the worms is based on the observation of several unstained and stained preparations and eight series of sections made through various planes.

Townsend (1935) has described the egg of Synthesiomyia nudiseta and recorded the interesting fact that the larva forms a cocoon. The larval stages and the puparium do not appear to have been described. That this species was not among the larvae of some unknown muscids described by Banks (1912) is evident from the figures of the-posterior spiracles. The present communication provides an account of all the early stages.

Malaria is endemic over a wide area of the earth's surface. Although popularly associated with tropical or subtropical countries, it occurs as far north as the south of Sweden and Lake Ladoga in Russia and as far south as Bechuanaland, Swaziland and Natal in South Africa and the Argentine in South America. Though most frequent in low-lying districts it may be found at altitudes as great as 6000–9000 ft.

Our knowledge of this interesting group of mites has been built up by the writings of some twenty-two acarologists, of different nationalities, whose papers are published in some four or five languages and have appeared in thirty to forty journals.

1. A new species of the genus Rhabditis is described.

2. The development of a standard method of culturing the species is outlined, and the effect on the nematode of varying the method of culturing is detailed and discussed.

3. The relationships between the nematode and the bacteria and Protozoa of the cultures are discussed.

The writer wishes to express his deep gratitude to Prof. A. D. Hobson, for his invaluable advice and assistance at all stages. Thanks are also due to King's College, the University of Durham, for financial assistance in the form of a Post-Graduate Studentship.

Through the courtesy of Prof. Ali Akhtar, Afghanistan, the writer examined about eight flukes obtained from the trachea of the spoon-bill, Platalea leucorodia var. major. A short account is given of the species, and its affinities are discussed below.

1. The osmotic pressure of the medium in which the nematodes were cultured has been shown to be equivalent to that of about 30 mM. NaCl.

2. The effects of immersion in a saline solution isotonic with the above, in glass-distilled water, and in hypertonic saline solutions, have been described. Particular attention was paid to changes in the length of the body, in the appearance and behaviour of the alimentary canal, and in the movement of the body.

3. The results obtained have been discussed, and the following tentative conclusions reached:

(a) The main aqueous exchanges occur through the cuticle and protoplasm covering the periphery of the body, and are controlled by the protoplasm rather than by the cuticle. The cuticle thus does not act as aja impermeable outer covering which insulates the animal from its environment.

(b) The species normally lives in an environment which is hypotonic to the body fluids, and maintains its internal osmotic pressure by means of an active method of osmotic regulation. The alimentary canal is probably partially, but not wholly, responsible for this regulation.

(c) Swelling occurs in distilled water because the removal of water in the initial stages is not rapid enough to cope with the extra inflow. Later the excess water is removed.

(d) In concentrated solutions, water is removed from the body, and the internal osmotic pressure may also be increased to some extent by the penetration of osmotically active substances to the body, through the cuticle and hypodermis of the body wall. Penetration through the hypodermis is slower than through the cuticle.

(e) During recovery in concentrated solutions, there is a slow removal of osmotically active material from the body. The hypertrophy of the lateral and post-anal organs, which sometimes occurs under these conditions, may be connected with this removal.

1. Aphidius matricariae Hal. is an internal parasite of Myzus persicae Sulz.; it was also found parasitizing M. circumflexus Buckt. and Aulacorthum solani Kalt. (Myzus pseudosolani Theob.).

2. The percentage of aphides successfully parasitized increased with an increased number of strikes per host. A single female can lay up to 350 eggs, and one female successfully parasitized 309 M. persicae.

3. The female parasite reaches its maximum activity during the 2nd or 3rd day of oviposition, and this activity has no correlation with light intensity.

4. The disappearance of supernumerary larvae due to cannibalism has been observed.

5. The species is arrhenotokous. Mating takes place from 2 hr. after emergence. In the progeny of early matings the females preponderated; in later matings the sex ratio was approximately 1:1.

6. The parasite appears to fly under the same conditions as those generally favourable for aphides. It is generally disseminated by flight of the adult itself and through localized movements of parasitized apterous aphides.

7. The host is unable to reproduce if ‘struck’ in the 3rd instar or earlier.

Two vivax-like parasites, believed to be true P. vivax but in abnormal form, are described. The deviation from normal appearances was probably due, it is suggested, to growth in an abnormal environment.

Among a very large number of preparations reputed to possess mosquito-repellent properties, only a few are really efficacious. The most commonly used preparations are those prepared with citronella oil. Definite information, however, on the comparative efficiency of many of these preparations is lacking. It was therefore our object to determine the value of different culicifuges under laboratory conditions. The experimental results obtained in this connexion are sufficiently promising to justify their publication, especially because owing to the war the want of an effective and a cheap culicifuge is all the more important.

1. The homonym Styphlodora compactum Dawes, 1941, has been renamed S. compressa.

2. Several suggestions have been made regarding the invalidity of proposed species of the genus Styphlodora. S. compactum Byrd, Parker & Reiber, 1940, should be regarded as a synonym of S. bascaniensis Goldberger, 1911, S. natricis as a synonym of S. magna Byrd & Denton, 1938, S. agkistrodontis as a synonym of S. floridanis Byrd, Parker & Reiber, 1940, S. lachesidis as a synonym of S. horridum (Leidy, 1850).

3. A suggestion has been made to relegate the proposed genus Paurophyllum Byrd, Parker & Reiber, 1940, to synonymity with the genus Styphlodora Looss, 1899. The proposed new species Paurophyllum simplexus and P. megametricus Byrd, Parker & Reiber, 1940, are identical and should be known as Styphlodora simplexa (Byrd, Parker & Reiber, 1940a) n.comb. S. aspina Byrd, Parker & Reiber, 1940, is a synonym of this species.

4. A revised key to the sixteen apparently valid species of the genus Styphlodora has been constructed. S. floridanis and S. simplexa have been found places in it provisionally, though it is suggested that further study of the trematode parasites of the kidney of Agkistrodon piscivorus might result in the merging of these species into a single species, namely, Styphlodora simplexa (Byrd, Parker & Reiber, 1940).

The developmental stages of Braula coeca are described. The larva is an inquiline living in a tubular burrow which it makes by mining on the inner side of the capping of the honey cells in the comb of the hive bee. It is meta-pneustic and bears characteristic anterior and posterior girdles of sensoria.

The pupa is apparently unique among Cyclorrhapha in that it is enclosed within the unmodified cuticle of the 3rd instar larva, no puparium being formed. It is suggested that this feature is a degenerative change owing to the cessation of a particular phase of hormone activity.

The similarity of form and structure shown by the larvae of Braula and of the Chamaemyiidae (Ochthiphilidae) is indicative of a fundamentally close relationship. Their imagines on the other hand have undergone widely divergent evolution.

A turkey brought to this laboratory for examination in 1934 was found to be harbouring protozoal parasites in the red blood cells, but the parasite was not definitely identified at the time. The parasite was determined as a Plasmodium species by Mr R. Daubney when he returned from leave; and when Dr Carlton Herman was a guest worker at thia Institute in 1939 Mr Daubney suggested that he might like to investigate the incidence of this particular parasite in turkeys in the neighbourhood of Kabete. A visit was then made to a nearby turkey farm, and blood smears taken from many poults. One of these birds proved to be infected with a Plasmodium. Using the blood of this bird, experimental infection was set up in other young turkeys.

1. The carcasses of 154 silver foxes of various ages, from fifteen farms in the southwest, have been examined and their parasites recorded. In addition, those of fourteen wild red foxes have similarly been examined.

2. The incidence of various species of nematode, cestode, and protozoan parasites has been analysed for the foxes, in age groups and in farm groups.

3. The worm egg counts in the faeces have been discussed in relation to the numbers of female worms in the foxes. No adequate correlation has been established between the two sets of data.

4. The ages of the foxes at incidence of the nematode parasites has been discussed, and the possibility of the development of resistance to various species investigated.

5. Certain peculiarities in the sex ratios of the Nematoda have been discussed.

6. The possibility of infestation of silver foxes by parasites derived from the wild-red-fox population of the neighbourhood of the farms has been investigated, as has also that of the transference of Crenosoma striatum from the hedgehog to foxes.

During the last few years I have successfully used a new method for investigating intestinal amoebae in cultures, and in the hope that it may also prove serviceable to other workers I now propose to describe it. At the same time I take the opportunity of noting two new staining methods which I have used especially in conjunction with this technique, but which are of general utility in protozoology and cytology.

The louse populations of the heads of 93 infested children, 45 boys and 48 girls under 14 years of age from a northern English industrial city have been examined.

The average number of lice per head was 14·8 for all children, 12·7 for boys and 16·8 for girls. The maximum population observed was 142.

The majority of infestations (65%) were light with under 10 lice. Girls were more frequently heavily infested than boys.

Most of the infestations, though light, must have been established at least for some weeks.

Using the method developed by VanOrden & Nelson (1926) in withdrawing and examining cloacal contents of four captive individuals of the Plathander or clawed frog (Xenopus laevis), the writer determined that infections of ciliate protozoans had persisted for more than 6 years.

1. Experiments are described in which various concentrations of pyrethrum in oil are tested for speed of stimulation of Ornithodorus larvae. There is a logarithmic relation between concentration and speed of stimulation, except with concentrated solutions (stronger than 0·015% by weight of pyrethrin I) in which there is a relative retardation of response.

2. As larvae grow older they respond more slowly, and this is probably due to an increase in thickness of the cuticle in natural growth.

3. Mineral oils induce much swifter penetration of the pyrethrum than any of the vegetable oils tested.

My thanks are due to Prof. Buxton in whose department the work was done, and also, to Dr J. T. Martin of Rothamsted Experimental Station, who kindly analysed samples of Pyremist ‘L’ for pyrethrin I.

Members of the genus Trichuris Roederer, 1761 (Syn. Trichocephalos Goeze, 1782; Trichocephalus Schrank, 1788) have a characteristic shape. The oesophageal portion of the body is very slender and is longer than the posterior portion, the latter being usually much stouter than the former. The eggs are lemon-shaped with a knob at each end, while the egg-shell is of a dark brown colour when seen in faeces.

In this paper two new genera of Laelaptidae are raised, the first for four large mites taken oh a banded mongoose, the second to fit a number of females taken on a squirrel. In addition to these new genera, two new species of Liponyssus and a new species of Haemolaelaps are described. All these specimens have been collected in Uganda.