Adult. Eyeless; camerostome without movable cheeks. In size (largest specimen 14 × 9 mm., Smallest 9 × 6 mm.), configuration, grooves, etc strongly recalling O. coriaceus, and the younger specimens have a suggestion of a similar dorsal pattern, but the whole surface is uniformly mammillate and the hood and the rather long palps are visible from the dorsal aspect. Discs in most specimens inconspicuous. Basis capituli about as broad as long, broadest posteriorly, where there are short, stiff, caducent bristles (? three pairs) directed outwardly. Hypostome lanceolate, with very small corona, followed by 2/2 well spaced teeth, about 6 per row. The leg armature, best understood from Text-fig. 1, is highly characteristic, the most striking feature being a prominent, rather sharp tooth on the proximal false articulation of the tarsus in legs I, II and III, but absent on tarsus IV. All the tarsi bear a prominent dorsal tooth near their distal ends. Legs I and II show characteristic prominences on other articles, notably the penultimate, which has a dorsal tooth at its basal and distal extremities.

The present paper is the first of a series describing a collection of cestodes from the Biological Laboratory of the Egyptian Government School of Medicine, Cairo, the nematodes having previously been described in this Journal by Baylis (1923 a, 1923 b, 1923 c) and Boulenger (1926). The identification of this portion of the collection has presented great difficulties, the specimens, from long immersion in alcohol mixed with fragments of cork, having become so pigmented as to be virtually black and almost unstainable: but for a formula (soak for 3 to 5 days in pure beechwood creosote, then transfer for the same time to 5 per cent. hydrochloric acid in 70 per cent, alcohol) supplied by Dr H. A. Baylis—to whom the author tenders his most sincere thanks—the elucidation of their anatomy would have been impossible.

The material for this investigation was obtained from the intestines of cormorants shot on the coast of Cardigan Bay between Aberystwyth and Borth. Of 23 birds examined, 5, or 23 per cent., were infected with this species. Anything from 1–10 individuals were obtained from each intestine.

Balantidium coli (from the domestic pig) can be readily cultivated in the medium devised by Dobell and Laidlaw (1926) for the cultivation of entozoic amoebae (inspissated horse-serum and Ringer-eggwhite, with solid rice-starch). If the hydrogen-ion concentration does not exceed the limits p H = 5·4–8·0, rich cultures can be obtained in this medium, at 37° C.; and strains of the ciliate can be readily propagated for any desired period if subcultures are made every 3–5 days.

In such cultures conjugation occurs periodically; but encystation has never been observed, and all attempts to induce it under cultural conditions have hitherto failed.

The conjugation of Balantidium, as seen in cultures, is peculiar, but it has been impossible as yet to elucidate all details of the process. Conjugants are always much smaller than non-conjugants, and frequently unequal in size. Apparently but one conjugant is fertilised, and survives as an exconjugant—the partner dying after separation.

Encystation has never been seen to follow conjugation, as described by Brumpt (1909).

1. Crepidostomum farionis inhabits the gall bladder, as well as the intestine and pyloric caeca, of the trout and grayling.

2. The life history of Crepidostomum farionis has been worked out and is based on the similarity of organisation of the cercaria, encysted larval trematode and the adult.

3. The first intermediate hosts in the life history of this trematode are Pisidium amnicum (Müll.) and Sphaerium corneum (L.) though the latter is unusual.

4. The second intermediate host is the larva of the mayfly, Ephemera danica (Müll.).

5. There are two generations of rediae, the first gives rise to daughter rediae, which in turn produce cercariae.

6. The rediae are characterised by the absence of ambulatory processes and a functional intestine.

7. The cercaria (n.sp.) possesses “eye spots,” stylet and gland cells (salivary?), and the excretory vesicle is tube-shaped.

8. The excretory system of the redia and the cercaria has been worked out in detail.

9. The relation of the parasites to their respective hosts is discussed. On account of the need for further observations definite conclusions are held over for a later paper.

A mouse, which had been intraperitoneally injected with a filtered, diluted, cellular suspension of mouse-adeno-carcinoma, three months afterwards, was found to have developed a tumour of the same type on the pyloric end of the stomach surface, adherent to a cyst of the liver, containing the strobiloid larval stage of Taenia crassicollis.

Thirty-five other mice, similarly injected, but which were not infected with this cestode, did not develop growths in the peritoneum.

In the course of a study of the bionomics of Hylemyia (Chortophila) brassicae Bouché, the Cabbage Root Fly, a small number of adults of this and a closely allied species were observed in the field to possess a somewhat unusual appearance. The capture and subsequent microscopical examination of these flies showed that they were parasitised by a micro-organism, which appears to be a fungus.

In cestodes of this family, the number, size, and shape of the rostellar hooks is needed for the identification of the species. While number and size are often quoted (e.g. Fuhrmann, 1924 a) the shape is usually ignored owing to the impossibility of reproducing innumerable figures: this greatly lessens the usefulness of such lists as the one above mentioned, especially to workers not in touch with a well-stocked library. For this reason the formula illustrated in Text-fig. 1 is suggested. The base, AB, of the hook is considered as unity and other measurements are expressed in decimals of it. EH is a tangent drawn parallel to AB and touching the hook at its highest point H; GB, FC and KL are perpendiculars drawn from AB to the two extremities G, F of the hook and to the inside, K, of the curve FG. With the points A, G, H and K fixed the approximate shape of the hook is determined: the various formulae may then be compared or the hook itself be reconstructed. Text-fig. 2 gives examples of the various types of hooks and their respective formulae, Text-fig. 3 of their reconstruction from the formulae. This arrangement appears preferable to that of Stevenson (1904) as being simpler and also facilitating reconstruction.

Female characters. Head connected to the thorax by a V-shaped chitinised plate. Eyes absent. Antennae 5-jointed, the first segment strongly developed. Thorax long and narrow; metathorax distinct. Sternal plate present, long and narrow; metasternum with narrow transverse chitinised bar. Thoracic stigmata apparently absent. Fore pair of legs smaller than the mid and hind legs; mid and hind legs sub-equal, widely separated. Abdomen elongated and narrow, without sutures and tergal and sternal plates. Pleural plates present on the second abdominal segment only. Stigmata present on the third to eighth abdominal segments. Tergites and sternites each with a row of long hairs and short spines.

Nos connaissances sur le cycle chromosomique et la meïose des Grégarines conduisent à deux interprétations tout à fait opposées, et il est difficile, à l'heure actuelle, de décider laquelle est exacte. II est vraisemblable que l'une et l'autre contiennent une part de vérité, et que, à cet égard, les Grégarines ne présentent peut-être pas une homogénéité complète. Si l'on ne tient pas compte de la chronologie de nos connaissances concernant la réduction chromatique des Grégarines, on peut classer comme suit les conclusions des quelques auteurs qui ont entrepris cette étude.

Dans le pus des ulcérations du gros intestin on trouve toujours en nombre plus ou moins considérable des macrophages d' un type spécial. On tencontre ces macrophages dans la dysenterie bacillaire, dans la dysenterie amibienne, dans le colitis ulverosa (cette dernière a, pour moi, une origine non infectieuse).

The monocystid here described was found in the coelom of Pheretima heterochaeta (Mich.).

The following account is based wholly on material fixed in vapour of osmic acid and methyl alcohol—other fixatives like Bouin's and Schaudinn's gave bad results.

The rich material of Ixodoidea in our Museum, which I have recently studied, enables me to give records of the geographical distribution of some genera. The genus Dermacentor of the vast Russian territory, as I have shown elsewhere, is represented by two widely distributed species, D. reticulatus and D. niveus. The collection contains specimens from the following localities.

Linnaeus (1747) described and figured (reproduced in Fig. 1) a parasitic Copepod from the gills of a Gadus, which he designated Lernaea cauda duplici tereti, and defined in these words: Thorax seu corpus molle, album, subrotundum, convexum, carnosum; antice obtusum, seu potius retusum, latere utroque notatum, denticulo molle antrorsum spectante. Collum tenue longiusculum, caput trilobum dilatatum; lobo intermedio obverse eordato. Cauda pone thoracem ex duobus corpusoulis pallidis longitudine thoracis. Brachia sub thorace, ad latera colli utrinque duo, quorum pars exterius bilobum, interius ovatum.

The Trematode parasites of man have been so frequently listed and, for the most part, so fully described in various text-books and treatises on parasitology, pathology and tropical medicine that it might seem superfluous to enumerate them again. My object in doing so is to provide a basis for comparison with the parasites of the Primates, our knowledge of which is still extremely fragmentary, and with the parasites of Mammals in general. It is hoped that the works which are cited will prove to be the most useful or the most authoritative original references available.