Each year the study of Diptera reveals some new and often unexpected facts concerning the mode of life of their early stages. The rich entomological literature dealing with this subject clearly shows that the diversity of conditions under which the larvae of this order of insects live surpasses that of any other order of the Animal Kingdom.

1. A study has been made of the adult female Sarcoptes scabiei de Geer var. hominis (Hering). The findings have been compared to the description of Sarcoptes of the horse given by Buxton.

2. Forty-two living adult female S. scabici de Geer var. hominis (Hering) have been measured.

3. The apparent increase in size due to mounting is demonstrated.

4. The anatomy of the birth passage is discussed with special reference to the absence, in the specimens examined, of a genital operculum.

The following is a summary of our studies on population of head lice, adults and nits.

1. Out of a total of 8702 adult lice, the male population comprised 2031. The gross infestation rate per head was 129.9 and the maximum number found on a single head was 1434. A disproportion in the distribution of the two sexes was a marked feature.

2. Patients below the age of 11 showed a lower infestation rate than those above this age, and short-haired individuals were more heavily infested than long-haired ones.

3. Frequent combing of the hair and the use of oil did not seem to dislodge the adults or to prevent the females from laying eggs.

4. The maximum larval count on a single head was found to be 4260, the average number of larvae per single head was 418·8, and 9 to 1 was the maximum proportion of larvae to females.

5. The maximum number of nits on a single hair was found to be 17 and 5·06 was calculated as the average number per hair.

6. Treatment with kerosene and pyrethrum killed all the lice and nits, and reinfestation did not occur.

7. The infestation did not spread to healthy patients in the hospital ward; it is thought that the poor migratory habits of lice are responsible for this.

8. From studies on the reinfestation of an individual after treatment it is concluded that head-lice cannot establish themselves on any part of the body except the head, and if their access to the head is prevented, the lice will not survive for more than 24 hr.

1. The spores of Eimeria (not the oocysts) are the real infective agents and, as in other Sporozoa, they readily set free their sporozoites in the duodenum or in vitro under suitable conditions.

2. The protective oocyst has double walls: the ectocyst is thick and impervious to fluids but easily fractures by mechanical means, such as drying. Even though cracked, it may continue to protect the thin endocyst and spores until they reach the specially muscular regions of the alimentary canal. Free spores are probably also sometimes ingested.

3. The ectocyst is a continuous envelope without a persistent micropyle. It resembles keratin in many ways.

The present paper includes two sections of a proposed series on the lungworms of the Odontoceti or toothed whales. Only members of the family Delphinidae among the Odontoceti have so far been reported as hosts to these lungworms.

The first section deals with the systematic relationships of the lungworms of the Odontoceti. They are held to constitute a family Pseudaliidae in the superfamily Metastrongyloidea. The nature of the female reproductive system and specifically of the ovejectoral apparatus in the suborder Strongylina is discussed and the concept expressed that the organization of the latter structure is of phylogenetic and taxonomic importance in this group. On the basis of variations in the ovejectoral apparatus three families of strongyline lungworms (except for Syngamus v. Siebold, 1836) are recognized—Dictyocaulidae Skriabin, 1941, Metastrongylidae Leiper, 1909, and Pseudaliidae Railliet, 1916.

The second section deals with the genus Halocercus Baylis & Daubney, 1925. Previous literature is reviewed. A key and table of measurements for the known species are presented. H. invaginatus (Quekett, 1841) Dougherty, 1943, is redescribed, and H. kirbyi n.sp. named and described.

During the handling of about 10,000 ticks in the course of insecticidal tests many abnormalities of the legs were encountered. Most of the cases were deficiencies due to the partial regeneration of a leg damaged in the previous nymphal stage. Two cases of special interest were not deficiencies, but exhibited supernumerary segments of leg.

1. A method for examining conditions governing anthelmintic activity in the small intestine is described. Nippostrongylus muris in the rat was the test organism and hexylresorcinol and C2C14 were the drugs examined.

2. The efficiency of hexylresorcinol was reduced by 50% in 1% sodium tauroglycocholate which reached a concentration of 1·3% in the rat small intestine. The adsorption of this drug on mucin reduced its concentration in intestinal fluids and prevented penetration to parasites under mucus. These inhibiting factors account for the inactivity of hexylresorcinol in the rat.

3. Tetrachlorethylene, which stimulated N. muris to leave mucus and enter fluids in the intestinal lumen, was not inhibited by bile salt and was found to act rapidly in the rat.

4. Sodium laurate activated hexylresorcinol more efficiently than sodium oleate at pH. 6·5. Both soaps showed intrinsic anthelmintic properties.

5. The results obtained in examining the rate of movement of fluids down the intestine and the effects of detergents, bile salts, mucin and ascorbic acid on drug activity are discussed.

1. The inactivation by γ-rays of tobacco mosaic virus is studied at various concentrations. It is found that the inactivation dose is independent of concentration at high concentrations, and at low concentrations also attains a constant, but lower, value. Over an intermediate range the inactivation dose increases with increase of concentration.

2. These facts are explained on the basis that when irradiated dry or in concentrated solution the inactivation is direct and due to ionization produced inside the virus particle. At lower concentrations the inactivation is largely indirect and due to ionization of the water.

3. Gelatin added to the solution protects the virus against the indirect action of radiation.

4. Curves are given of the inactivation of dry preparations of ribonuclease and adenylpyro-phosphatase (myosin) by X-rays.

5. It is shown that on the assumption that a single ionization in an enzyme molecule leads to its inactivation, measurement of the inactivation dose leads to a rough estimate of the molecular weight of the enzyme.

6. There appears to be no fundamental difference in the mechanism of radiation-inactivation of viruses and enzymes.

All irradiations were carried out at the Strangeways Laboratory. The virus was prepared and tested at the Plant Virus Station and the Molteno Institute. The enzymes were prepared and estimated at the Biochemical Laboratory. We are indebted to the British Empire Cancer Campaign for defraying the cost of the X-ray equipment at the Strangeways Laboratory.

Reasons are given for rejecting a recent proposal to change the names Anisakis simplex to Capsularia marina, Anisakis to Capsularia, Anisakinae to Capsulariinae and Porrocaecum decipiens to P. piscium. The question of the possibility of identifying the larval forms of Ascaridae occurring in fishes is discussed.

The main features of the life-history of Mermis nigrescens, so far as it is known, are briefly discussed. Some data have been collected on its distribution in the British Isles, and on the seasonal appearance of the egg-laying females. The insect hosts of the worm are discussed, and feeding experiments on various invertebrates are recorded, including the experimental infection of the common earwig (Forflctila auricularia). This insect, which has also been found naturally infested, is regarded as an important host for the species, more especially where grasshoppers are absent. Observations by other workers on the influence of the number of larvae per host on the sex of the developing worms, and on the survival of the host, have been confirmed. Two new species, closely related to M. nigrescens, are described: M. kenyensis and M. tahitiensis, from Africa and Tahiti respectively.