In 1916, the writer (Van Cleave, 1916) called attention to the fact that lack of published records should not be taken as an indication of scarcity of Acanthocephalans in the Chinese fauna. A single species of Centrorhynchus has been described from a magpie, and Faust (1921 a) has recorded the species common in the hog. As yet, apart from these two specific identifications, the acanthocephalan fauna of China has remained unknown.

1. A Heteromita species, probably Heteromita globosa, is described and the methods of culture and observation are detailed.

Heteromita globosa is a flagellate with a karyosome nucleus. The karyosome body is an achromatic structure. The chromatin lies on or around the periphery of the karyosome as a narrow diffuse layer and is also distributed upon the inner side of the nuclear membrane. There are two unequal flagella which arise from two blepharoplasts which are situated close together at the anterior end of the body. The blepharoplasts are connected with the nuclear membrane by fine rhizoplasts.

2. The division, encystation and excystation of the flagellates are described from living and stained material. The nuclear division is characterised by a well-developed spindle and the chromatin is arranged in an equatorial plate at the metaphase. The blepharoplasts play the part of centrosomes in the division of the nucleus.

3. The normal division in the living state takes 7 to 15 minutes. The blepharoplasts can be seen to separate, the nuclear space becomes hyaline and ceases to refract in the characteristic way, the space elongates, the blepharoplasts each with the flagellum attached come to lie at opposite poles of the elongating organism and a second flagellar rudiment can be seen to arise at each end alongside of the original one. The nuclei can be observed to reconstruct and the protoplasmic body draws apart rapidly, leaving a narrow protoplasmic junction which breaks through and the two daughter individuals separate.

4. A process of delayed division was observed. If after the division of the nucleus and the drawing apart of the main bulk of the protoplasm the actual breaking of the narrow junction between the two daughters fails to take place immediately, there seems to be no means of effecting this actual separation until the occurrence of a new nuclear division.

In the course of a few hours, usually 3 to 6, a second division occurs and each nucleus undergoes mitosis and the creature splits into four daughters.

The double individuals may encyst and when they emerge they do so as a single binucleate protozoan equipped with a double flagellar apparatus.

5. Syngamy has not been observed.

This species has received so few notices from collectors of parasitic Copepoda that it might be judged uncommon. Thus Krøyer (1837), originally placed it in the genus Lernaeopoda having but a single specimen at his disposal the host of which he had forgotten; subsequently it has been recorded by Olsson (1869), who was the first to place it correctly in the genus Brachiella. This species has also been recorded by P. J. van Beneden (1870), by T. Scott (1901), by A. Scott (1904), and collected by L. Harrison Matthews, as mentioned by me (1926), at Plymouth.

The present paper is the fifth instalment of the Report on the Molteno Institute collection, of which Parts I–III (Ascaeidae, Heterakidae, Oxyuridae, Camallanidae, etc.) and Part IV (Trichostrongylidae and Strongylidae) were published in this Journal by Dr H. A. Baylis (1923) and myself (1926). This collection was sent to Cambridge by Dr E. Hindle and consisted chiefly of unnamed material which had accumulated in the Parasitological Laboratory of the Egyptian Government School of Medicine in Cairo. Since commencing the work on the Filarioidea contained in this material, a further series of worms belonging to this order was placed at my disposal by the Cairo Medical School and the results of my study of this collection have been incorporated with those of the Molteno Institute specimens.

Owing to the kindness of Dr H. A. Baylis I have recently had the opportunity of examining portions of two species of Avitellmine tapeworms, both of which are new to Helminthology and both of which belong to a genus which is distinct from the two genera which have hitherto represented the Avitellininae. The material which I have examined is the property of and is deposited in the British Museum (Natural History) at South Kensington, London.

1. In vitro work on intestinal protozoa, employing the latest culture methods, seems to approach very closely to the normal conditions in the gut of the host.

2. Balantidium coli is readily cultivated in a medium composed of an inspissated horse-serum slope covered with Ringer's solution to which egg-albumen and starch are added.

3. Tested in this medium ipecacuanha and its alkaloids emetine and cephaeline show a considerable degree of toxicity.

4. Isoemetine, methylpsychotrine and demethoxyemetine are not toxic.

5. Arsenic compounds are not very toxic, atoxyl being the most toxic of those tried and stovarsol hardly at all toxic.

6. Colloidal silver compounds are at best feebly toxic.

7. Quinine is very feebly toxic.

8. There is evidence of a distinct correspondence between B. coli and E. histolytica in their reaction to certain drugs.

Recently (1927) I described a peculiar fungus parasitic on the fore-legs of a termite under the name Ectomyces calotermi n.g., n.sp. Unfortunately, I at the time overlooked a paper by Thaxter (1920), in which, among other fungus parasites of insects, he described the genus Termitaria which he founded for two species of a fungus parasitic on termites, and which appears to be the same as Ectomyces. I considered Ectomyces to be an Ascomycete; but Thaxter, who studied living material at different stages, says that the apothecial-like fructification arises by vertical proliferation from a primary pseudo-cellular layer of much branched and closely septate hyphae, some cells of which become modified and assume a chlamydospore-like appearance; and that the spores are successively abstricted as endo-conidia, and, in one species, are expelled through a terminal pore. Consequently, he considers it to be a Fungus Imperfectus of uncertain affinities, and apparently occupying an isolated position in the group Leptostromaceae.

Most compilers of our standard publications on parasitic Copepoda have described or figured species in an obviously mutilated condition, i.e. lacking the head or egg-strings.

1. The most striking successes with the method of biological control by the introduction of the parasitic and predaceous enemies of foreign pests, appear to have been obtained mainly in island areas; some doubt exists concerning the utility of the method in continental areas.

2. Three main objections may be raised to the use of the method of parasitic introduction in continental areas. The first is based on the similarity between the faunas and floras of such continental areas as Europe and North America, the second on the polyphagous habit of many parasites, the third on the behaviour of hyperparasites in relation to introduced primaries.

3. The studies made on the natural control of indigenous species in continental areas show that control is effected by complexes of many factors differing both quantitatively and qualitatively in the different parts of the habitat.

4. This fact appears at first sight to indicate the inutility of many of the factors involved, as, for example, the parasitic enemies.

5. The answer to this difficulty is to be found principally in the fact that the quantitative and qualitative fluctuations in the composition of the controlling complexes are much less important than they appear.

6. The effect of the disappearance of controlling factors of the two main types from controlling complexes of various kinds, is studied in detail in order to make this clear.

7. The action of many factors is thus shown to be much less important than it appears at first sight. Nevertheless, this action is real and to a certain degree indispensable in a given environment. The disappearance of a factor from a system in equilibrium will thus permit the increase and spread of the host.

8. The effects which follow the introduction of foreign pests in continental areas constitute a clear demonstration of their escape from control.

9. The evidence indicates that the factor whose absence has permitted increase and spread is the parasitic factor.

10. Equilibrium can be re-established in several ways. Mechanical methods must not be neglected and will normally interfere very little with the biological method; but it is to the latter method that we must turn for a hope of permanent and inexpensive control.

11. The practical results obtained by parasite introduction in continental areas tend in general to support the ideas defended in this paper, and justify the introduction of the native parasites and predators of foreign pests even in the case of exchanges between continental areas.

Whilst studying the development of Fasciola hepatica, I observed that the “collar” of the redia was rarely so prominent as it was figured and described by Thomas (1883). This observation, and a consideration of the mechanical requirements of the case, led me to suggest (1927) that Thomas was incorrect when he attributed to this structure the function of maintaining the circular section of the redia.

Larvae of Xenopsylla cheopis, which had been preserved at various dates from the first to seventeenth day after hatching, were placed at my disposal by Professor J. H. Ashworth. They were mounted for examination in excavated slides in carbol alcohol.

Attempts to cure general paralysis of the insane by infection with Spirochaeta duttoni have been made by Plaut and Steiner (1919), Mühlens and Kirschbaum (1921). Solomon, Berk, Theiler and Clay (1926) have reported upon the employment of Spirillum minus (Spirella morsus-muris) for the same purpose. The experiments referred to met with an encouraging measure of success; for the ultimate results have been comparable with those following therapeutic inoculation with malarial parasites.