The following report deals with a considerable collection of Nematodes made by Prof. A. S. Pearse, of Duke University, Durham, N.C., U.S.A., in various parts of Nigeria, and very kindly sent by him to the writer for study and determination.

(1) Examination of the inmates of Government reformatories in the Highlands of Kenya showed a high incidence (57·9 per cent.) of very light infestations with hookworm, and an incidence of approximately 50 per cent, of Taenia infestations. Many of the latter are not detected by the usual microscopic examination.

(2) Treatment with carbon tetrachloride in doses of from 1½c.c. for children to 4 c.c. as the standard adult dose gave approximately 76·1 per cent, cures for hookworm, and in the case of boys with fairly light infestations with T. saginata an efficacy of approximately 97 per cent. In the case of 72 boys very heavily infested with Taenia 58 per cent. cures were effected by a single treatment with carbon tetrachloride and oil of chenopodium.

(3) A combination of carbon tetrachloride and oil of chenopodium appears to be a safe and efficacious anthelminthic for the common worm infestations of man in Kenya.

(4) Growing natives lightly infested with hookworm appeared to grow and increase in weight at a normal rate, and did not improve in physical condition after treatment.

(5) Boys in the same institution infested with Taenia progressed at a subnormal rate, but increased to a figure above normal after treatment, the increase appearing to be mathematically significant in spite of the small number of samples analysed.

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.

Among Helminth material collected in the Sudan by the late Dr A. J. Chalmers, I have found some eight or nine mounted specimens of a Cestode, from the intestine of Gyps rüppelli, which has not, so far as I am aware, yet been described, and which apparently belongs to a new genus.

In 1926 two of us published the results of a long series of experiments on the toxic action of the alkaloids of ipecacuanha in cultures of several species of entozoic amoebae. These experiments led us to definite conclusions regarding the differential susceptibility of the various species of amoebae studied, and the relative potency of several alkaloids employed. They also showed clearly that the full specific action of emetine, on susceptible amoebae, is only disclosed if the alkaloid is allowed to act for a sufficient time (two or three days.)

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.

A few specimens very badly preserved and pigmented: coating them was a deposit which entirely obscured the internal anatomy and could not be removed. The internal anatomy therefore could not be removed. The internal anatomy therefore could not be elucidated. Length 10*, greatest breadh 0·47. Scolex 0·54 dia. As the only species without a rostellum recorded from this host is A. vaginatus the specimens are listed under that name.

Material examined. A male and a female from Ramphastos brevicarinatus, Barro Colorado Island, Panama Canal Zone, collected by Mr J. Van Tyne of the University of Michigan, through whose kindness I have been enabled to examine them. The species was originally described from “probably Ramphastos tocard” (which is R. brevicarinatus) from Colombia. My material agrees with the original description and is probably correctly identified, although, as will be further considered, another species of the same genus occurs upon toucans.

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.

The genus Crenosoma was founded by Molin in 1861 for two species of nematodes, Strongylus canis vulpis Rud., 1819, from the lungs of a fox (Vulpes vulpes L.), and Strongylus striatus Zeder, 1800, from the bronchi of a hedgehog (Erinaceus europaeus L.).

There is still so much confusion with regard to the minute hexapod mites which have for ages plagued man in various parts of the world, and which are known popularly as harvest bugs, harvest mites, bête rouge, rouget, chigger mites, etc., that a review of our present knowledge of the matter may be of use in saving investigators' time in referring to a voluminous and widely scattered literature.

The modern history of the group of parasites of which this paper relates begins with the unfortunate publication on the same day—December 28th, 1899—of two simultaneous revisions of the Trematoda by Looss and Lühe, which has led to endless confusion and difficulties of nomenclature. In the present instance both writers described new genera under the same name—Telorchis—placing in each somewhat similar assemblages of species, yet not sufficiently close in character to be accepted as synonymous genera; at the same time each writer wisely selected a type species and thereby rendered the task of unravelling this knot in systematics very easier. The position will be at once apparent on comparing the two descriptions, and in order to facilitate this I have rearranged the translated clauses of each so that they appear in the same order:

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.