The helminths dealt with in the present paper were recovered from an Indian chukar, Alectoris graeca chukar, brought in for examination by Major H. O. Pugh, D.S.O., Glandyfi, Cardiganshire, on 21 April 1938. The bird was one of several which were brought over from India in December 1937, and which were kept in captivity up to the date of examination of the bird under consideration. The death of this bird was found to be due to entero-hepatitis caused by Histomonas meleagris (Smith, 1895).

Amongst the collections of mites that have been sent to me for identification I have recently found six new species which are described and figured in the present paper.

In Part I the musculature of the internal organs of the male blow-fly, C. erythrocephala, testis, vas efferens, accessory gland, vas deferens, and ejaculatory sac and duct, is described, together with the movements observed in them and the passage of secretions down the system. It is suggested that the testicular and accessory gland secretions are ejaculated separately. The musculature, mechanics and co-ordinated movements of the external organs and associated structures are also described.

In Part II the generative organs of the female, except the ovaries, with special reference to their musculature and movements, and the musculature of the ovipositor are described and compared with those of M. domestica. It is suggested that the male accessory gland secretion is kept separate from the testicular secretion, the former passing into the lateral sacs of the female and the latter into the spermathecae.

In Part III the relation of the parts of the two sexes during coitus is discussed.

1. T. axei eggs in sheep faeces hatch at a temperature of 38° C. and a relative atmospheric humidity of 29%, but all of the larvae are dead 96 hr. after the initiation of the exposure. Eggs kept in faeces at −7° C. are killed within 96 hr.

2. Eggs do not hatch while under water but remain viable for 20 days under 15 mm. of water at temperatures ranging from 11 to 28° C. Under natural conditions the longevity would in all probability be influenced by such factors as depth of water, amount of decomposing organic debris, etc., which determine the amount of available oxygen present.

3. Completely embryonated eggs in sheep faeces possess a high resistance to drying. It is apparent that ranges and pastures in California cannot be freed of eggs by keeping suitable hosts off them during a single dry season, because the eggs can survive desiccation for a period exceeding the dry season. It is possible, however, that if the eggs were directly exposed to the rays of the sun they might be killed.

4. The non-infective larvae of T. axei are very much less resistant to desiccation than are the eggs. The population of non-infective larvae would, however, under the more common natural conditions, normally attain the infective stage before succumbing to desiccation.

5. Infective larvae lived for more than 104 days at a temperature of 38° C. and a relative atmospheric humidity of 29%. At −7° C. they were alive at the end of 25 days but were dead on the thirty-ninth day. It is believed that under natural conditions such larvae would not be exterminated by high temperatures. At low temperatures the usual covering of snow might sufficiently protective to prevent death.

6. T. axei infective larvae survived 230 days' submergence in 5 mm. of water at room temperature in diffused daylight. Direct sunlight appears have some lethal effect. The amount of oxygen available in the water appears to determine to a considerable degree the longevity of the larvae. Under natural conditions infective larvae can survive even greatly prolonged flooding.

7. The survival of infective larvae to desiccation is dependent upon the actual degree of dryness attained. Larvae dried on glass slides at room temperature ranging from 17 to 27° C. with a relative atmospheric humidity of from 35 to 51% survived up to 16 days after the initiation of exposure.

8. Different investigators have obtained different results in studying the longevity of infective larvae in soil. The writers believe that the infective larvae do not spend much time on soil or migrate through it unless to escape some unfavourable environmental factor such as particularly high or low temperatures or desiccation, or unless they are accidentally washed into it during heavy rainfall.

9. No evidence of phototropic behaviour was observed. It is believed that vertical migration up vegetation is caused by a negatively geotropic reaction which may be conditioned or altered at times by stronger external stimuli resulting from extreme temperatures, bright sunlight, low atmospheric humidity, etc.

10. It is believed that the seasonal incidence of trichostrongylosis on irrigated ladino clover pastures in California is determined by acquired resistance, age resistance, or both.

11. A mixture of a 1% solution of 40% nicotine sulphate and 1% copper sulphate appears to be a more efficient anthelmintic against T. axei than a straight 1% copper sulphate solution. Changing from green feed to hay or rendering hay available along with green feed may possibly have a therapeutic effect. Spontaneous recovery, so far as clinical symptoms are concerned, from an acute trichostrongylosis, without the administration of a drug or changing the diet, seems to be common, if not the rule, in the majority of lambs in an infected band.

When eggs of Monieza expansa are fed to galumnid mites, the onchospheres emerge in the intestine and migrate to the body cavity. Here they undergo metamorphosis and develop into cysticercoids. The dissection of mites, at various intervals after exposure, has yielded a successive series of developmental stages. Protocols of the experiments and photographs of living larvae are presented. These results demonstrate that mites serve as intermediate hosts of Moniezia, and probably also of other anoplocephaline cestodes.

During a study of syrphid larvae I met with several instances of their being parasitized by hymenopterous larvae. The species of syrphid larvae most commonly parasitized, in my material, was Sphaerophoria flavicauda. From the puparia of this species I obtained two species of ichneumonids, which Mr J. F. Perkins, of the Natural History Museum, London, very kindly identified for me as Bassus tetragonus Thunb. and Homocidus fissorius Grav. Out of seven puparia of Sphaerophoria flavicauda, one adult of Homocidus fissorius and six of Bassus tetragonus were obtained. This paper therefore deals mainly with the larvae of the latter species.

1. Several behaviouristic and physiological differences distinguish the two species Trichogramma semblidis and T. evanescens (tabulated on p. 514).

2. There are no true intermediates between the two forms of the male T. semblidis, but intermediate types are simulated by degenerate individuals of small size produced by starvation.

3. Among 1740 males reared from eggs of Sialis and 1847 reared from eggs of moths, there were only nineteen exceptions to the rule that the apterous form emerges from the former and the winged form from the latter.

4. The ability of T. semblidis to produce its apterous male can remain latent through as many as sixty-four generations reared on Sitotroga and yet find its full expression immediately when the parasite is reared on Sialis.

5. Several other species of Neuroptera have been parasitized, but Sialis lutaria remains the only known host that regularly elicits the apterous form.

6. T. semblidis is capable of arrhenotokous parthenogenesis. The statement that the species includes thelytokous strains requires corroboration.

1. Pimpla ruficollis is a parasite of the pine shoot moth Rhyacionia (Evetria) buoliana Schiff. (Eucosmidae) which emerges from its host a considerable time before the next generation of larvae are ready for oviposition. It seems that during this period the parasites leave the pine trees and feed on the flowers of certain Umbelliferae and probably other plants. Only after 3 or 4 weeks do they return to the pine trees where the shoots now contain larvae ready for egg laying.

2. It has been shown by means of olfactometer experiments that during this first period of the adult life, the parasites are repelled by the odour of oil of Pinus sylvestris. At this time the ovaries are very small and are probably not ready for the production of eggs. After the third or fourth week of life the females become attracted by the oil of P. sylvestris and the ovaries are now relatively large.

3. Since Geraniol is known to be a constituent of certain conifers, this substance was also tested. It was, however, found to be invariably repellent to the parasites.

4. There is some evidence that conclusions reached as a result of experiments with P. ruficollis also apply to the ophionine ichneumonid Eulimneria rufifemur.

An account is given of two aberrant strains of Trypanosoma evansi recovered from Sudanese camels.

One of these—like the four other ones described in a previous paper—was totally akinetoplastic (= akinetonucleate) and has been kept under observation for eighteen months in the course of which the aberrant condition remained unchanged.

The second strain was characterized by a wide fluctuation in the proportion of akinetoplastic forms which ranged from zero to over 70% at different periods of observation.

The bearing of this fluctuation upon the production of akinetoplastic strains is discussed and it is concluded that these probably arise in nature either indirectly, through the inoculation by the insect vector of new hosts with trypanosomes lacking the kinetoplast, or directly, by the strain becoming totally akinetoplastic within the same host.

From an analysis of the fluctuating strain it would appear that the variation in the proportion of akinetoplastic trypanosomes depends upon the following factors: (1) irregular division (without bipartition of the kinetoplast), which is the most important factor; (2) rate of reproduction of normal and aberrant individuals; (3) mortality rate of the different types of dividing and non-dividing forms.

The primary cause of the disappearance of the kinetoplast could not be ascertained.

Two nucleoproteins with similar chemical composition have been isolated from the leaves of tobacco plants infected with tobacco necrosis virus. One of these is crystalline and has a sedimentation constant of 130 × 10−13; the other is amorphous and its principal component has a sedimentation constant of 58 × lO−13.

Each preparation will infect plants at a dilution of 1 in 108 and will precipitate specifically with antiserum at a dilution of 1 in 3·2 × 105.

The nature of the difference between preparations in the two states is obscure and it has not proved possible to convert the one into the other.